García Ruano José L, Fraile Alberto, Martín M Rosario, Núñez Alberto
Departamento de Química Organica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
J Org Chem. 2006 Aug 18;71(17):6536-41. doi: 10.1021/jo060990s.
The Rh2(OAc)4-catalyzed reactions of o-(methoxycarbonyl)-alpha-diazoacetophenone with enantiomerically pure 5-ethoxy-3-p-tolylsulfinylfuran-2(5H)-ones 1a and 1b afford 4,10-epoxybenzo[4,5]cyclohepta[1,2-c]furan-3,9-diones 6a and 6b, in good or moderate yields and in a completely regioselective way. The pi-facial selectivity is complete for 1a, which only yields anti-6a adducts, and very high for 1b. The endo stereoisomers are favored with respect to the exo ones in both reactions. The sulfinyl group significantly increases the reactivity of the dipolarophile as it has been demonstrated by studying the behavior of 5-methoxyfuran-2(5H)-one (3).
Rh2(OAc)4催化的邻（甲氧基羰基）-α-重氮苯乙酮与对映体纯的5-乙氧基-3-对甲苯亚磺酰基呋喃-2(5H)-酮1a和1b反应，以良好或中等的产率且完全区域选择性地得到4,10-环氧苯并[4,5]环庚[1,2-c]呋喃-3,9-二酮6a和6b。对于1a，π-面选择性是完全的，只生成反式-6a加合物，对于1b则非常高。在两个反应中，内型立体异构体相对于外型立体异构体更受青睐。如通过研究5-甲氧基呋喃-2(5H)-酮（3）的行为所证明的，亚磺酰基显著提高了亲偶极体的反应活性。
