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