Several phosphepine oxides were synthesised in optically pure form. Sharpless asymmetric dihydroxylation was used to introduce the chiral centres in all cases. Ring closure was achieved using either PhPCl2 or PrPCl2 together with a double nucleophile generated by either a double ortho-lithiation or double bromineâlithium exchange. The X-ray crystal structures of three phosphepine oxides illustrate their different conformations. The NMR spectra of several phosphepine oxides are described as is the chemistry which is shown to differ from that of acyclic phosphine oxides.
Novel thiepines were synthesised using a Sharpless asymmetric dihydroxylation reaction to introduce the two chiral centres and with ring closure achieved by using sulfur diimidazole in conjunction with either a double ortho-lithiation or a double bromine/lithium exchange.
Synthesis of homochiral dibenzo[b,f]phosphepin 5-oxides using a double ortho-lithiation strategy
作者:Stuart Warren、Paul Wyatt
DOI:10.1016/0957-4166(96)00099-7
日期:1996.4
Enantiomerically pure chiral seven membered phosphorus heterocycles - phosphepins - have been prepared by McMurry coupling, Sharpless dihydroxylation, ortho-lithiation and reaction with PhPCl(2) or PrPCl2. Studies of the ortho-lithiation and of hydrolysis of phosphepinium salts are included. Copyright (C) 1996 Elsevier Science Ltd
Synthesis and chemistry of enantiomerically pure 10,11-dihydrodibenzo[b,f]thiepines
作者:Paul Wyatt、Andrew Hudson、Jonathan Charmant、A. Guy Orpen、Hirihattaya Phetmung
DOI:10.1039/b516606c
日期:——
Several chiral thiepines were efficiently constructed using sulfur diimidazole in combination with a variety of bislithiated carbon fragments. The sulfur atom in these thiepines is found to be unusually unreactive compared to diphenylsulfide.