Chirale 1,3,2-Oxazaborolidine aus chiralen 2,3-Dihydro-1H-1,3,2-diazaborolen und Diphenylketen
作者:L. Weber、A. Rausch、H.-G. Stammler、B. Neumann
DOI:10.1002/zaac.200500054
日期:2005.7
Reaction of equimolar amounts of diphenylketene with 1,3-di-tert-butyl-2-isobutyl-2,3-dihydro-1H-1,3,2-diazaborole tBuNCH=CHN(tBu)B-iBu (1) regioselectively afforded 1,3,2-oxazaborolidine tBuN-CH(CH=NtBu)C(=CPh2)OB-iBu (2). The employment of a series of chiral diazaboroles (S,S)-Me(Cy)CHNCH=CH-NCH(Cy)Me}BX (3a: X = nBu; b: nBu; c: CH2SiMe3; d: NHtBu) led to the formation of the diastereoisomeric oxazaborolidines
等摩尔量的二苯基乙烯酮与 1,3-二叔丁基-2-异丁基-2,3-二氢-1H-1,3,2-二氮杂硼 tBuNCH=CHN(tBu)B-iBu (1) 反应区域选择性地得到1,3,2-氧杂硼烷 tBuN-CH(CH=NtBu)C(=CPh2)OB-iBu (2)。使用一系列手性重氮杂硼 (S,S)-Me(Cy)CHNCH=CH-NCH(Cy)Me}BX (3a: X = nBu; b: nBu; c: CH2SiMe3; d: NHtBu)导致非对映异构体氧氮杂硼烷 Me(Cy)CHN-CHCH=NCH(Cy)Me)C(=CPh2)OBX (4a-d) 与非对映体过量 de 的形成,其随着来自 de 的 X 的空间需求而增加= 55% (X = nBu) 至 de >= 95% (X = NHtBu)。在可比较的条件下,用乙烯酮处理对映体纯二氮杂硼 (S)-tBuNCH=CHN(tBu)B-NHCH