Due to their straightforward syntheses and promising host-guest properties, organic macrocycles received lots of scientific attention, especially in supramolecular, medicinal and material communities. Ever since the seminal discovery of crown ethers in the mid-1960s, there is a steady increase in research interest towards new types of macrocycles, and the quest for new applications from these host molecules, including more classical ones, such as cyclodextrin, calix[n]arene, etc. and more recent ones, such as Stoddart's blue-box, Flood's cyanostar, Ogoshi's pillar [n]arene, cycloparaphenylenes from a collective effort from Bertozzi, Jasti and Itami, etc, (Scheme 1a). They are further employed as building blocks for more complex architectures, including cages, molecular machines, extended frameworks, and polymers. Despite these advances, one general drawback for macrocycles reported so far is their lack of versatility as building blocks to other kinds of macrocycles. That is, once they are synthesized, their inherit macrocyclic structures/classes are fixed and unamenable to post-synthetically modification (PSM) to other classes of macrocycles. Nevertheless, PSM organic macrocycles are rare in literature. Recently, Wang showed that resorcin[n]arenes can be applied in the precise construction of carbon nanobelts (Scheme 1b). Most contemporary organic macrocycles are arene-based molecules that are produced from petroleum-based commodity chemicals. Therefore, their mass production would come along considerable environmental burden. One the other hand, biomass-based feedstocks, such as furfural, and other furfural-derived chemicals, have long been considered the most promising sustainable non-fossil building blocks for the future production of fuels, chemicals, and eventually replacing fossil feedstocks in industry. Besides, their high industrial values stem from their potential transformation, via a two-step sequence namely cycloaddition with a proper dienophile followed by aromatization, into important benzenoid commodity chemicals, such as terephthalic acid and its derivatives, and more recently, polyaromatic hydrocarbons (PAH). We hypothesize that a furan-based macrocycle, derived from biomass feedstock, would behave as a "macrocyclic template" that can be "late-stage" post-synthetically modified into macrocycles with different benzenoid structures with a tailor-made pre-determined ring size (Scheme 1d). Previously, Kohnke and Hart attempted the transformation from substituted calix[n]furans to pillar[n]arenes through a [4+2] cycloaddition/deoxygenative aromatization pathway with benzyne precursors. Disappointingly, complete furan-to-arene transformation was unsuccessful. We attributed this limitation to steric crowdedness around all the furan units within a macrocyclic confinement. We herein report this unusual macrocycle-to-macrocycle-to-macrocycle transformation from a common unsubstituted calix [4]furan (1) as building block to a wide range of pillar [4]naphthalenes (2) and even a pillar [4]anthracene macrocyle (3) for the first time, via pillar [4](1,4-epoxynapthalene) intermediates ( ). Collectively, our new approach opens up a viable path using biomassderived macrocyclic templates to access benzenoid-based macrocycles inaccessible by conventional methods (Scheme 1c). RESULTS AND DISCUSSION Unlike substituted calix[n]furans, research progress on calix [4]furan (1) equipped with unsubstituted methylene linker is slow mainly due to a lack of effective synthetic strategies, as its conversions were consistently <3% (Table ). To overcome this historic synthetic challenge, we developed a revised synthetic path to calix [4]furan (1) and greatly enhanced its synthetic practicality. As shown in Table , we re-evaluated different reaction conditions, including furan (Figure ) and methylene precursors (entry 5) and stoichiometry (entry 2-4), Lewis acid catalysts (entry 5, 8-11), and additives (entry 5, 13-18). After optimization, the best condition to form 1 is using difurylmethane (5) and formaldehyde (CH2O)n (6a) (0.1 equiv.) with Hf(OTf)4 as catalyst (0.25 mol%) and LiOTf as a templating agent in acetonitrile (0.14 M) for 96 h. Under this condition, 1 can be obtained in 24% yield, detected by GC analysis and an isolated yield of 13% yield was achieved (Table , entry 5). During our investigation, we discovered that the successful formation of 1 requires a delicate balance between reagent choice and very specific reaction condition, or else the formation of 1 would be strongly disfavored. Notably, replacing 6a with dimethoxymethane (6b), a formaldehyde surrogate, under the same reaction condition gave 1 in only 2% yield (Table , entry 5). Although reaction concentration is known to affect reaction rate, to our surprise, increasing (0.21 and 0.35 M) or decreasing reaction concentration (0.07 M) away from the optimum concentration (0.14 M) would completely shut down the reaction (Table , entries 6-7). Furthermore, employing LiOTf as a templating agent is key to the formation of 1, as reactions without LiOTf or with other metal salts, such as LiCl, LiTFSI (TFSI = bis(trifluoromethane)sulfonimide) and NaOTf failed to give 1 in 2% yield (Table 1, 12-15).