Synthesis of 2,2',2'',2'''-(1,2-ethanediylidene)tetrafuran and diel-alder reaction with dimethyl acetylene-dicarboxylate

摘要

A one step procedure has been found that converts 2,2',2'',2'''-methylenedifuran (1) into 2,2',2'',2'''-(1,2-ethanediylidene)tetrafuran (4: 1,1,2,2-tetrakis(furan-2-yl)ethane). This compound adopts two similar C_(2v)-symmetrical conformations (4A and 4A') in the crystalline state in which the C-H bond of the 1,2-ethanediylidene moieties is anti-periplanar with the C(2)-O bond of the vicinal furan-2-yl groups. Tetrafuran (4) is little reactive toward dienophiles with normal electronic demand. With dimethyl acetylenedicarboxylate a single 1:1 adduct (8) (dimethyl (1RS,2RS,2aRS,5RS,5aRS,6RS,8aRS,8bSR)-1,2-di(furan-2-yl)-1,2-dihydro-5H,6H-2a,5:6,8a-diepoxyacenaphthylene-5a,8b-dicarboxylate) was isolated. its structure was established by single crystal X-Ray radiocrystallography.