Stereoselective Synthesis of P-Chirogenic Dibenzophosphole–Boranes via Aryne Intermediates
摘要:
A new aryne-mediated tandem cross-coupling/P-cyclization sequence starting from tertiary phosphine-boranes and 1,2-dibromobenzenes is reported. P-chirogenic dibenzophospholes become accessible in a regio-, chemo-, and diastereoselectiye way.
Efficient Stereoselective Synthesis of <i>o</i>-Functionalized P-Chirogenic Phosphines Applied to Asymmetric Catalysis
作者:Jérôme Bayardon、Sylvain Jugé
DOI:10.1080/10426507.2014.993760
日期:2015.6.3
The stereoselective synthesis of P-chirogenic o-halogenophenylphosphines and their use for the preparation of o-functionalized derivatives are reported. The key step of this synthesis is based on the reaction of a P-chirogenic secondary phosphine borane, previously prepared using ephedrine methodology, with n-butyllithium (1.2 equiv.) and 1,2-dihalogenobenzene. The reaction proceeds by addition of the phosphide borane to the benzyne generated in situ from 1,2-dihalogenobenzene by metal-halide exchange with the intermediate carbanion. The o-halogenophenylphosphine boranes were obtained with retention of configuration at the P-center and with enantioselectivities up to 99% ee. The free o-halogenophenylphosphines were applied for the preparation of various kinds of o-functionalized P-chirogenic phosphines useful in asymmetric catalyzed reactions.