α-Ketophosphonates as Ester Surrogates: Isothiourea-Catalyzed Asymmetric Diester and Lactone Synthesis
摘要:
Isothiourea HBTM-2.1 catalyzes the asymmetric Michael addition/lactonization of aryl- and alkenylacetic acids using alpha-keto-beta,gamma-unsaturated phosphonates as alpha,beta-unsaturated ester surrogates, giving access to a diverse range of stereodefined lactones or enantioenriched functionalized diesters upon ring-opening.
α-Ketophosphonates as Ester Surrogates: Isothiourea-Catalyzed Asymmetric Diester and Lactone Synthesis
摘要:
Isothiourea HBTM-2.1 catalyzes the asymmetric Michael addition/lactonization of aryl- and alkenylacetic acids using alpha-keto-beta,gamma-unsaturated phosphonates as alpha,beta-unsaturated ester surrogates, giving access to a diverse range of stereodefined lactones or enantioenriched functionalized diesters upon ring-opening.
NHC-mediated enantioselectiveformal [4+2] cycloadditions of alkylarylketenes with γ-substituted-β,γ-unsaturated α-ketophosphonates is described. A substrate-dependent switch in diastereoselectivity was observed, with γ-aryl α-ketophosphonates providing preferentially the syn-dihydropyranone-phosphonates and γ-methyl α-ketophosphonates favouring the anti-dihydropyranone-phosphonate. In addition, ketene generation