The reaction conditions and product distributions are shown in Figure . note that the stereochemistry of the 1-propenyl groups was maintained in the reactions of 5 and 6 , and presumably 7. From these product distributions were calculated the percent of each intermediate, 13-16, that were converted to the cycloaddition products 8-9 and 11-12 (Figure ). One should also note that for the cis-1-propenyl intermediates 15 and 16, unexpectedly more cis-cyclobutane product 12 was formed from the initially formed trans-intermediate 15 than from the initially formed cisintermediate 16.