Yang Jinchao, Farley Alistair J M, Dixon Darren J
Department of Chemistry , Chemistry Research Laboratory , University of Oxford , 12 Mansfield Road , Oxford , UK . Email:
Chem Sci. 2017 Jan 1;8(1):606-610. doi: 10.1039/c6sc02878k. Epub 2016 Sep 14.
The highly enantioselective sulfa-Michael addition of alkyl thiols to unactivated β-substituted-α,β-unsaturated esters catalyzed by a bifunctional iminophosphorane (BIMP) organocatalyst is described. The low acidity of the alkyl thiol pro-nucleophiles is overcome by the high Brønsted basicity of the catalyst and the chiral scaffold/thiourea hydrogen-bond donor moiety provides the required enantiofacial discrimination in the addition step. The reaction is broad in scope with respect to the alkyl thiol and β-substituent of the α,β-unsaturated ester, affords sulfa-Michael adducts in excellent yields (up to >99%) and enantioselectivity (up to 97 : 3 er) and can operate down to 1 mol% catalyst loading.
描述了由双功能亚胺基膦烷（BIMP）有机催化剂催化的烷基硫醇对未活化的β-取代-α,β-不饱和酯的高度对映选择性硫醚-迈克尔加成反应。催化剂的高布朗斯台德碱性克服了烷基硫醇亲核前体的低酸度，并且手性骨架/硫脲氢键供体部分在加成步骤中提供了所需的对映面识别。该反应在烷基硫醇和α,β-不饱和酯的β-取代基方面具有广泛的适用范围，以优异的产率（高达>99%）和对映选择性（高达97:3的对映体过量）提供硫醚-迈克尔加合物，并且在低至1 mol%的催化剂负载量下也能进行。
