Furans

A rhodium-mediated carbene addition is the key step in a synthesis of furans. The precursors were synthesized on TentaGel-NH2 resin, which was transformed into an amide 94. Subsequent formation of imides 95 with malonylchloride and reaction with tosylazide gave solid phase-bound diazoimides 96. Reaction with Rh2(OAc)4 in presence of electron-deficient acetylenes produced substituted furans 98 via the intermediate isomiinchnone 97 and a sequence of a [2+3]-cycloaddition to the acetylene and an subsequent cycloreversion sequence. The yields of the reaction varied from 50 % to 70 % (Scheme 26) [37], o nh2

R1-COOH, DIC, DMAP DMF

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