Chemoselectivity as a Delineator of Cuprate Structure in Catalytic 1,4-Addition of Diorganozinc Reagents to Michael Acceptors
作者:Matthias Welker、Simon Woodward、Luis F. Veiros、Maria José Calhorda
DOI:10.1002/chem.200903310
日期:2010.5.17
of this SR‐protected 1,4‐benzoquinone has been compared with the behavior of the analogous OR‐protected acetal in copper‐catalyzed additions of ZnMe2 by using chiral phosphoramidite ligands. The activation energy for 1,4‐methylation of the latter OR‐acetals with ZnMe2 (>95 % ee) has been determined for two CuX2 pre‐catalysts (X=OAc, 12.2 kcal mol−1; X=OTf, 6.7 kcal mol−1; Tf=triflate). The dithioacetal
的反应环状硫缩醛(RS)2 CHCHO [R = 1/2× (CH 2)3 ]与HCCCOMe,随后用的TsCl / DABCO(TS =甲苯磺酰基,DABCO = 1,4-二氮杂双环[2.2.1治疗。 2]辛烷)制得单保护的1,4-苯醌二硫缩醛。通过使用手性亚磷酰胺配体,将这种SR保护的1,4-苯醌的反应性与类似的OR保护的乙缩醛在铜催化的ZnMe 2加成物中的行为进行了比较。对于后者OR-缩醛与ZnMe的1,4-甲基化的活化能2(> 95% ee值)已被确定为2的CuX 2预催化剂(X = OAC,12.2千卡摩尔-1; X = OTf,6.7kcal mol -1;Tf =三氟甲磺酸盐)。在铜的存在下,二硫缩醛SR aromatizes我/ ZnMe 2得到1,4- HOC 6 H ^ 4 S(CH 2)3 SMe的至C S键的形成。这两种密切相关的底物的不同行为是根据紧