Reaction of 4-R-2-phenyltetrahydrobenzo[b]pyrylium and 9-R-sym-octahydroxanthylium salts with furfural and related compounds
The condensation of furfural, 5-methylfurfural, and 2-thiophenecarbaldehyde with 4-R-2-phenyltetrahydrobenzo[b]pyrylium and 9-R-sym-octahydroxanthylium salts was studied. Condensation conditions under which acidophobic aldehydes of the furan series do not undergo resinification were found. 8-Furfurylidene and 8-thenylidene derivatives of 4-R-2-phenyltetrahydrobenzo[b]pyrylium and bisfurfurylidene and bisthenylidene derivatives of 9-R-sym-octahydroxanthylium salts were obtained for the first time.