Complementary diastereoselectivity in the intermolecular addition of titanium and magnesium naphtholates to asymmetric lactaldehydes
作者:Robin G. F. Giles、Cynthia A. Joll、Melvyn V. Sargent、D. Matthew G. Tilbrook
DOI:10.1039/a901456j
日期:——
S)-2-(1′-ethoxyethoxy)propanal 4 afforded solely (1S, 2R, 1″R or S)-1-(7′-benzyloxy-4′,5′-dimethoxy-1′-hydroxy-2′-naphthyl)-2-(1″-ethoxyethoxy)propan-1-ol 5, being the erythro product arising from anti addition. Complementary reaction of the naphthol 3 as its bromomagnesium naphtholate with aldehyde 4 gave rise solely to the alternative (1R, 2R, 1″R or S) diastereomer 6 . The naphthol 3 was prepared through the completely
的7-苄氧基-4,5-二甲氧基-1-萘酚3作为其triisopropoxytitanium萘酚(2加成- [R,1' - [R或小号)-2-(1'-乙氧基乙氧基)丙醛4只得到(1小号,2 - [R,1“ R或S)-1-(7'-苄氧基-4',5'-二甲氧基-1'-羟基-2'-萘基)-2-(1”-乙氧基乙氧基)丙-1-醇5,是反添加产生的赤字产物。萘酚3作为萘甲酸溴镁与醛4的互补反应仅产生了另一选择(1 R,2 R,1“ R或S)非对映体6。通过将2-甲氧基呋喃9完全区域选择性地加成到5-苄氧基-3-甲氧基脱氢苯8中来制备萘酚3。从香兰素中方便地制备了这种差异保护的双烷氧基苯并zy。