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= = original design = =

the type 1 gold dollar depicts a head of liberty facing left with a coronet or tiara on her head bearing her name her hair is gathered in a bun she is surrounded by 13 stars representing the original states the reverse features the date and denomination within a wreath with the name of the nation near the rim
contemporary reviews of the type 1 design were generally favorable the new york weekly tribune on may 19 1849 described the new dollar as undoubtedly the neatest tiniest lightest coin in this country it is too delicate and beautiful to pay out for potatoes and sauerkraut and salt pork oberon might have paid puck with it for bringing the blossom which bewitched titania willis ' bank note list stated that there is no probability of them ever getting into general circulation they are altogether too small the north carolina standard hoped that they would be struck at the charlotte mint and circulated locally to eliminate the problem of small @@ denomination bank notes from out of state coin dealer and numismatic author q david bowers notes that the head of liberty on the type 1 dollar is a scaled @@ down version of that on the double eagle and a nicely preserved gold dollar is beautiful to behold

= = modifications = =

mint records indicate the first gold dollars were produced on may 7 1849 longacre 's diary notes state instead that the first were struck on may 8 a few coins in proof condition were struck on the first day along with about 1 @@ 000 for circulation there are five major varieties of the 1849 gold dollar from philadelphia made as longacre continued to fine @@ tune the design <unk> dies were sent by longacre 's engraving department at the philadelphia mint to the branch mints at charlotte dahlonega ( in georgia ) and new orleans coins struck at the branches resemble some of the types issued from philadelphia depending on when the dies were produced of the coins struck at the branch mints in 1849 only pieces struck at charlotte ( 1849 @@ c ) exist in multiple varieties most are of what is dubbed the closed wreath variety approximately five of the 1849 @@ c open wreath are known one believed the finest surviving specimen sold at auction for $ 690 @@ 000 in 2004 remaining a record for the gold dollar series as of 2013 one of the changes made during production was the inclusion of longacre 's initial l on the truncation of liberty 's neck the first time a us coin intended for full @@ scale production had borne the initial of its designer all issues beginning in 1850 bear the closed wreath beginning in 1854 the gold dollar was also struck at the new san francisco mint
the continued flow of gold from california made silver expensive in terms of gold and us silver coins began to flow out of the country for melting in 1849 a flow that accelerated over the next several years as the price of the metal continued to rise by 1853 a thousand dollars in silver coin contained $ 1 @@ 042 worth of bullion as silver coins vanished the gold dollar became the only federal coin in circulation between the cent and the quarter eagle ( $ 2 @@ 50 piece ) as such it was struck in large numbers and widely circulated according to bowers in his book on the denomination the years 1850 to 1853 were the high @@ water mark of the gold dollar the glory years of the denomination when the little gold coins took the place of half dollars and silver dollars in everyday transactions this time came to an end in 1853 when congress passed an act reducing the weight of most silver coins allowing new issues of them to circulate
as early as 1851 new york congressman william duer alleged that that patterson had made the gold dollar too small in diameter on purpose to provoke criticism patterson retired that year after 16 years in his position and under his successor george n eckert annular gold dollar and half dollar patterns were struck public ledger reported that although gold dollars would not be struck in annular form gold half dollars would be to help fill the need for change with the new pierce administration thomas m pettit took office as mint director on march 31 1853 in april treasury secretary james guthrie wrote to pettit that there were complaints that the gold dollar was too small often lost or mistaken for a small silver coin and enquiring about reports the mint had experimented with annular dollars pettit replied stating that none had been preserved but enclosed a silver piece of equivalent size he noted that while there would be technical difficulties in the production of the annular dollar these could be overcome in a letter dated may 10 pettit proposed an oval @@ shaped holed piece or an angular @@ shaped coin which would lessen the production problems pettit died suddenly on may 31 guthrie did not let the issue fall but queried pettit 's replacement james ross snowden concerning the issue on june 7 as us coins were required to bear some device emblematic of liberty the secretary hoped that artists could be found who could find some such design for an annular coin
the act of february 21 1853 that had lightened the silver coins also authorized a gold three @@ dollar piece which began to be produced in 1854 to ensure that the three @@ dollar piece was not mistaken for other gold coins it had been made thinner and wider than it would normally be and longacre put a distinctive design with an indian princess on it longacre adapted both the technique and the design for the gold dollar which was made thinner and thus wider an adaptation of longacre 's princess for the larger gold coin was placed on the dollar and a similar agricultural wreath on the reverse the idea of making the gold dollar larger in this way had been suggested in congress as early as 1852 and had been advocated by pettit but guthrie 's desire for an annular coin stalled the matter in may 1854 snowden sent guthrie a letter stating that the difficulties with an annular coin especially in getting the coins to eject properly from the press were more than trivial
nevertheless the type 2 gold dollar ( as it came to be known ) proved unsatisfactory as the mints had difficulty in striking the new coin so that all details were brought out this was due to the high relief of the design the three southern branch mints especially had trouble with the piece many of the type 2 pieces quickly became illegible and were sent back to philadelphia for melting and recoinage on most surviving specimens the 85 in the date is not fully detailed the type 2 gold dollar was struck only at philadelphia in 1854 and 1855 at the three southern branch mints in the latter year and at san francisco in 1856 after the design was designated for replacement to correct the problems longacre enlarged the head of liberty making it a scaled @@ down version of the three @@ dollar piece and moved the lettering on the obverse closer to the rim this improved the metal flow and design sharpness so much that early numismatic scholars assumed the reverse was also altered though in fact no change was made and the type 2 and type 3 reverses are identical

= = = design of type 2 and 3 dollars = = =

the type 2 and 3 gold dollars depict liberty as a native american princess with a fanciful feathered headdress not resembling any worn by any indian tribe this image is an inexact copy of the design longacre had made for the three @@ dollar piece and is one of a number of versions of liberty longacre created based on the venus <unk> or crouching venus a sculpture then on display in a philadelphia museum for the reverse longacre adapted the agricultural wreath he had created for the reverse of the three @@ dollar piece composed of cotton corn tobacco and wheat blending the produce of north and south this wreath would appear later in the 1850s on the flying eagle cent
art historian cornelius vermeule deprecated the indian princess design used by longacre for the obverses of the types 2 and 3 gold dollar and for the three @@ dollar piece the ' princess ' of the gold coins is a banknote engraver 's elegant version of folk art of the 1850s the plumes or feathers are more like the crest of the prince of wales than anything that saw the western frontiers save perhaps on a music hall beauty

= = war years = =

the gold dollar continued to be produced in the late 1850s though mintages declined from the figures of two million or more each year between 1850 and 1854 only about 51 @@ 000 gold dollars were produced in 1860 with over two @@ thirds of that figure at philadelphia just under a third at san francisco and 1 @@ 566 at dahlonega roughly a hundred are known of the last creating one of the great rarities from dahlonega in the series
the other candidate for the rarest from that mint is the 1861 @@ d with an estimated mintage of 1 @@ 000 and perhaps 45 to 60 known two pairs of dies were shipped from philadelphia to dahlonega on december 10 1860 they arrived on january 7 1861 two weeks before georgia voted to secede from the union as the american civil war began under orders from governor joseph e brown state militia secured the mint and at some point small quantities of dollars and half eagles were produced records of how many coins were struck and when have not survived since dies crack in time and all the mints were supplied with them from philadelphia coining could not last and in may 1861 coins and supplies remaining at dahlonega were turned over to the treasury of the confederate states of america which georgia had by then joined gold coins with a face value of $ 6 were put aside for assay normally they would have been sent to philadelphia to await the following year 's meeting of the united states assay commission when they would be available for testing instead these were sent to the initial confederate capital of montgomery alabama though what was done with them there and their ultimate fate are unknown the rarity of the 1861 @@ d dollar and the association with the confederacy make it especially prized
dahlonega like the other two branch mints in the south closed its doors after the 1861 strikings it and the charlotte facility never reopened the new orleans mint again struck coins from 1879 to 1909 but did not strike gold dollars again after 1861 the only issuance of gold dollars outside philadelphia was at san francisco in 1870
the outbreak of the civil war shook public confidence in the union and citizens began hoarding specie gold and silver coins in late december 1861 banks and then the federal treasury stopped paying out gold at face value by mid @@ 1862 all federal coins even the base metal cent had vanished from commerce in much of the country the exception was the far west where for the most part only gold and silver were acceptable currencies and paper money traded at a discount in the rest of the nation gold and silver coins could be purchased from banks exchange agents and from the treasury for a premium in the new greenbacks the government began to issue to fill the gap in commerce and finance the war

= = final years abolition and collecting = =

since gold did not circulate in the united states ( except on the west coast ) in the postwar period much of the production of coins of that metal in the united states was double eagles for export accordingly although 1 @@ 361 @@ 355 gold dollars were struck in 1862 the last time production would exceed a million the mintage fell to 6 @@ 200 in 1863 and remained low for the rest of the coin 's existence excepting 1873 and 1874 the mint felt it improper to suspend coinage of a coin authorized by congress and issued proof coins ( generally a few dozen to the tiny numismatic community ) from specially @@ polished dies also producing enough circulation strikes so that the proof coins would not be unduly rare in 1873 and 1874 old and worn gold dollars held by the government were melted and recoined generating large mintages of that denomination this was done in anticipation of the resumption of specie payments which did not occur until the end of 1878 once specie again circulated at face value the gold dollar found no place in commerce amid large quantities of silver coinage either released from hoarding or newly struck by the mint the government expected that the resumption of specie payments would cause the dollar and other small gold coins to circulate again but the public allowed to redeem paper currency continued to use it as more convenient than coins
in the 1870s and 1880s public interest grew in the low @@ mintage gold dollar collecting coins was becoming more popular and a number of numismatists put aside some gold dollars and hoped for increases in value the mint most likely channeled its production through some favored philadelphia dealers though proof coins could be purchased for $ 1 @@ 25 at the cashier 's window at the philadelphia facility banks charged a premium for circulation strikes they were popular in the jewelry trade mounted into various items the coins were often exported to china or japan where such jewelry was made the dollars were often damaged in the process the mint refused to sell into this trade and did its best to hinder it nevertheless mint officials concluded that jewelers were successful at getting the majority of each issue proof mintages exceeded 1 @@ 000 by 1884 and remained above that mark for the remainder of the series numbers likely inflated by agents of jewelers willing to pay the mint 's premium of $ 25 per coin another use for the gold dollar was as a holiday gift after its abolition the quarter eagle became a popular present
james pollock in his final report as mint director in 1873 advocated limiting striking of gold dollars to depositors who specifically requested it the gold dollar is not a convenient coin on account of its small size and it suffers more proportionately from abrasion than larger coins his successors called for its abolition with james p kimball before he left office in 1889 writing to congress that except as jewelry little practical use has been found for this coin later that year the new director edward o leech issued a report stating that the gold dollar is too small for circulation and [ is ] used almost exclusively for the purposes of ornament the last year in which the gold dollar was struck was 1889 congress abolished the gold dollar along with the three @@ cent nickel and three @@ dollar piece by the act of september 26 1890
a total of 19 @@ 499 @@ 337 gold dollars were coined of which 18 @@ 223 @@ 438 were struck at philadelphia 1 @@ 004 @@ 000 at new orleans 109 @@ 138 at charlotte 90 @@ 232 at san francisco and 72 @@ 529 at dahlonega according to an advertisement in the february 1899 issue of the numismatist gold dollars brought $ 1 @@ 80 each still in demand as a birthday present and for jewelry that journal in 1905 carried news of a customer depositing 100 gold dollars into a bank the teller aware of the value credited the account with $ 1 @@ 60 per coin in 1908 a dealer offered $ 2 each for any quantity as coin collecting became a widespread pastime in the early 20th century gold dollars became a popular specialty a status they retain the 2014 edition of rs yeoman 's a guide book of united states coins rates the least expensive gold dollar in very fine condition ( vf @@ 20 ) at $ 300 a value given for each of the type 1 philadelphia issues from 1849 to 1853 those seeking one of each type will find the most expensive to be a specimen of the type 2 with the 1854 and 1855 estimated at $ 350 in that condition the other two types have dates valued at $ 300 in that grade

= = commemorative gold dollars = =

the gold dollar had a brief resurrection during the period of early united states commemorative coins between 1903 and 1922 nine different issues were produced with a total mintage of 99 @@ 799 these were minted for various public events did not circulate and none used longacre 's design


= johnson corey chaykovsky reaction =

the johnson corey chaykovsky reaction ( sometimes referred to as the corey chaykovsky reaction or ccr ) is a chemical reaction used in organic chemistry for the synthesis of epoxides aziridines and <unk> it was discovered in 1961 by a william johnson and developed significantly by e j corey and michael chaykovsky the reaction involves addition of a sulfur ylide to a ketone aldehyde imine or enone to produce the corresponding 3 @@ membered ring the reaction is <unk> favoring trans substitution in the product regardless of the initial stereochemistry the synthesis of epoxides via this method serves as an important <unk> alternative to the traditional epoxidation reactions of olefins
the reaction is most often employed for epoxidation via methylene transfer and to this end has been used in several notable total syntheses ( see synthesis of epoxides below ) additionally detailed below are the history mechanism scope and enantioselective variants of the reaction several reviews have been published

= = history = =

the original publication by johnson concerned the reaction of 9 @@ <unk> <unk> with substituted benzaldehyde derivatives the attempted wittig @@ like reaction failed and a <unk> oxide was obtained instead noting that reaction between the sulfur <unk> and <unk> did not afford <unk> as had the phosphorus and arsenic <unk>
the subsequent development of ( <unk> ) methanide ( ch3 ) <unk> and ( <unk> ) methanide ( ch3 ) <unk> ( known as corey chaykovsky reagents ) by corey and chaykovsky as efficient methylene @@ transfer reagents established the reaction as a part of the organic canon

= = mechanism = =

the reaction mechanism for the johnson corey chaykovsky reaction consists of nucleophilic addition of the ylide to the carbonyl or imine group a negative charge is transferred to the heteroatom and because the sulfonium cation is a good leaving group it gets expelled forming the ring in the related wittig reaction the formation of the much stronger phosphorus @@ oxygen double bond prevents <unk> formation and instead <unk> takes place through a 4 @@ membered cyclic intermediate
the trans diastereoselectivity observed results from the reversibility of the initial addition allowing equilibration to the favored anti betaine over the syn betaine initial addition of the ylide results in a betaine with adjacent charges density functional theory calculations have shown that the rate @@ limiting step is rotation of the central bond into the conformer necessary for backside attack on the sulfonium
the degree of reversibility in the initial step ( and therefore the diastereoselectivity ) depends on four factors with greater reversibility corresponding to higher selectivity
stability of the substrate with higher stability leading to greater reversibility by favoring the starting material over the betaine
stability of the ylide with higher stability similarly leading to greater reversibility
<unk> hindrance in the betaine with greater hindrance leading to greater reversibility by <unk> formation of the intermediate and slowing the rate @@ limiting rotation of the central bond
<unk> of charges in the betaine by <unk> such as lithium with greater solvation allowing more facile rotation in the betaine intermediate lowering the amount of reversibility

= = scope = =

the application of the johnson corey chaykovsky reaction in organic synthesis is diverse the reaction has come to encompass reactions of many types of sulfur ylides with electrophiles well beyond the original publications it has seen use in a number of high @@ profile total syntheses as detailed below and is generally recognized as a powerful transformative tool in the organic repertoire

= = = types of ylides = = =

many types of ylides can be prepared with various functional groups both on the anionic carbon center and on the sulfur the substitution pattern can influence the ease of preparation for the reagents ( typically from the sulfonium halide eg <unk> iodide ) and overall reaction rate in various ways the general format for the reagent is shown on the right
use of a sulfoxonium allows more facile preparation of the reagent using weaker bases as compared to sulfonium ylides ( the difference being that a sulfoxonium contains a doubly bonded oxygen whereas the sulfonium does not ) the former react slower due to their increased stability in addition the <unk> by @@ products of sulfoxonium reagents are greatly preferred to the significantly more toxic volatile and odorous <unk> by @@ products from sulfonium reagents
the vast majority of reagents are <unk> at the ylide carbon ( either r1 or r2 as hydrogen ) <unk> reagents are much rarer but have been described
if the ylide carbon is substituted with an electron @@ withdrawing group ( ewg ) the reagent is referred to as a stabilized ylide these similarly to sulfoxonium reagents react much slower and are typically easier to prepare these are limited in their usefulness as the reaction can become prohibitively sluggish examples involving amides are widespread with many fewer involving esters and virtually no examples involving other ewg 's for these the related <unk> reaction is typically more appropriate
if the ylide carbon is substituted with an aryl or allyl group the reagent is referred to as a semi @@ stabilized ylide these have been developed extensively second only to the classical methylene reagents ( r1 = r2 = h ) the substitution pattern on aryl reagents can heavily influence the selectivity of the reaction as per the criteria above
if the ylide carbon is substituted with an alkyl group the reagent is referred to as an <unk> ylide the size of the alkyl groups are the major factors in selectivity with these reagents
the r @@ groups on the sulfur though typically <unk> have been used to synthesize reagents that can perform enantioselective variants of the reaction ( see variations below ) the size of the groups can also influence diastereoselectivity in <unk> substrates

= = = synthesis of epoxides = = =

reactions of sulfur ylides with ketones and aldehydes to form epoxides are by far the most common application of the johnson corey chaykovsky reaction examples involving complex substrates and ' exotic ' ylides have been reported as shown below
the reaction has been used in a number of notable total syntheses including the danishefsky taxol total synthesis which produces the chemotherapeutic drug taxol and the kuehne <unk> total synthesis which produces the pesticide strychnine

= = = synthesis of aziridines = = =

the synthesis of aziridines from <unk> is another important application of the johnson corey chaykovsky reaction and provides an alternative to amine transfer from <unk> though less widely applied the reaction has a similar substrate scope and functional group tolerance to the carbonyl equivalent the examples shown below are representative in the latter an <unk> forms in situ and is opened via nucleophilic attack to form the corresponding amine

= = = synthesis of <unk> = = =

for addition of sulfur ylides to enones higher 1 @@ 4 @@ selectivity is typically obtained with sulfoxonium reagents than with sulfonium reagents many electron @@ withdrawing groups have been shown compatible with the reaction including ketones esters and amides ( the example below involves a weinreb amide ) with further conjugated systems 1 @@ 6 @@ addition tends to predominate over 1 @@ 4 @@ addition

= = = other reactions = = =

in addition to the reactions originally reported by johnson corey and chaykovsky sulfur ylides have been used for a number of related homologation reactions that tend to be grouped under the same name
with epoxides and aziridines the reaction serves as a ring @@ expansion to produce the corresponding <unk> or <unk> the long reaction times required for these reactions prevent them from occurring as significant side reactions when synthesizing epoxides and aziridines
several cycloadditions wherein the ylide serves as a nucleophilic carbenoid equivalent have been reported
living <unk> using <unk> as the catalyst and ( <unk> ) methanide as the monomer have been reported for the synthesis of various complex polymers

= = <unk> variations = =

the development of an enantioselective ( ie yielding an enantiomeric excess which is labelled as ee ) variant of the johnson corey chaykovsky reaction remains an active area of academic research the use of chiral sulfides in a stoichiometric fashion has proved more successful than the corresponding catalytic variants but the substrate scope is still limited in all cases the catalytic variants have been developed almost exclusively for enantioselective purposes typical <unk> reagents are not prohibitively expensive and the racemic reactions can be carried out with equimolar amounts of ylide without raising costs significantly chiral sulfides on the other hand are more costly to prepare spurring the advancement of catalytic enantioselective methods

= = = <unk> reagents = = =

the most successful reagents employed in a stoichiometric fashion are shown below the first is a bicyclic <unk> that has been employed in the synthesis of the β @@ adrenergic compound <unk> ( dci ) but is limited by the availability of only one enantiomer of the reagent the synthesis of the axial <unk> is rationalized via the 1 @@ 3 @@ <unk> effect which reduces the nucleophilicity of the equatorial lone pair the conformation of the ylide is limited by <unk> strain and approach of the aldehyde is limited to one face of the ylide by steric interactions with the methyl substituents
the other major reagent is a camphor @@ derived reagent developed by <unk> aggarwal of the university of bristol both enantiomers are easily synthesized although the yields are lower than for the <unk> reagent the ylide conformation is determined by interaction with the bridgehead hydrogens and approach of the aldehyde is blocked by the camphor moiety the reaction employs a <unk> base to promote formation of the ylide

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