Studies on the terpenoids and related alicyclic compounds XXXIX. A synthesis of .ALPHA.-methylene-.GAMMA.-lactones fused to medium and large rings by intramolecular cyclization of formylated allyl halides.
作者:Kiyoshi NISHITANI、Masashi ISOZAKI、Koji YAMAKAWA
DOI:10.1248/cpb.38.28
日期:——
Carbocyclic rings fused to an α-methylene-γ-lactone unit were synthesized from ω-formylated β-ethoxycarbonylallyl halides (4a-g) through intramolecular cyclization by the use of a low-valent chromium reagent, prepared from CrCl3 and LiAlH4, in N, N-dimethylformamide. α-Methylene-γ-lactones fused to medium (eight-membered) or large (twelve-and fourteen-membered) ring system (5a, c and d) were synthesized by this method in good to fairly good yields. However, the formylated allyl halide (4b), expected to afford a ten-membered carbocyclic ring system, gave dilactones fused to a twenty-membered ring unit even under a high dilution reaction condition.
与α-亚甲基-γ-内酯单元融合的碳环是通过将ω-甲酰化的β-乙氧基碳酰丙烯卤化物(4a-g)在N,N-二甲基甲酰胺中与低价铬试剂(由CrCl3和LiAlH4制备)通过分子内环化反应合成的。通过这种方法,融合中环(八元环)或大环(十二元和十四元环)系统的α-亚甲基-γ-内酯(5a、c和d)以良好到相当好的产率合成。然而,预计能形成十元碳环系统的甲酰化丙烯卤化物(4b),即使在高稀释反应条件下也只给出了与二十元环单元融合的二内酯。