Enantioselective (Formal) Aza-Diels−Alder Reactions with Non-Danishefsky-Type Dienes
作者:Uttam K. Tambar、Sharon K. Lee、James L. Leighton
DOI:10.1021/ja104480g
日期:2010.8.4
Enantioselective (formal) aza-Diels-Alderreactions between acylhydrazones and non-Danishefsky-type dienes have been developed. The reactions are promoted by a simple and economical chiral silicon Lewis acid and are typically conducted at ambient temperature. Both glyoxylate- and aliphatic aldehyde-derived hydrazones may be employed, as may variously substituted dienes, leading to the synthesis of
Polyhalides as Efficient and Mild Oxidants for Oxidative Carbene Organocatalysis by Radical Processes
作者:Xingxing Wu、Yuexia Zhang、Yuhuang Wang、Jie Ke、Martin Jeret、Rambabu N. Reddi、Song Yang、Bao-An Song、Yonggui Robin Chi
DOI:10.1002/anie.201611692
日期:2017.3.6
Simple and inexpensive polyhalides (CCl4 and C2Cl6) have been found to be effective and versatile oxidants in removing electrons from Breslow intermediates under N‐heterocyclic carbene (NHC) catalysis. This oxidative reaction involves multiple single‐electron‐transfer (SET) processes and several radical intermediates. The α, β, and γ‐carbon atoms of aldehydes and enals could be readily functionalized
[PROBLEMS] To provide a novel method for the allylation of N-acylhydrazones by which enantioselectively allylated N-acylhydrazines can be efficiently obtained.
[MEANS FOR SOLVING PROBLEMS] A method for the production of enantioselectively allylated N-acylhydrazines represented by the general formula [3]:
[wherein R
0
is an optionally substituted hydrocarbon group, an optionally substituted heterocyclic group, or —COOR
1
(wherein R
1
is a hydrocarbon group); R
2
is acyl; R
3
and R
4
are each hydrogen, or one of R
3
and R
4
is hydrogen and the other is a hydrocarbon group; and R
5
and R
6
are each independently hydrogen or a hydrocarbon group], characterized by reacting an N-acylhydrazone represented by the general formula [1]:
[wherein R
0
and R
2
are as defined above] with an allylating agent such as allyltrichlorosilane or crotyltrichlorosilane in the presence of a chiral phosphine oxide.
[PROBLEMS] To provide a novel method for the allylation of N-acylhydrazones by which enantioselectively allylated N-acylhydrazines can be efficiently obtained.
[MEANS FOR SOLVING PROBLEMS] A method for the production of enantioselectively allylated N-acylhydrazines represented by the general formula [3]:
[wherein R° is an optionally substituted hydrocarbon group, an optionally substituted heterocyclic group, or -COOR1 (wherein R1 is a hydrocarbon group) ; R2 is acyl; R3 and R4 are each hydrogen, or one of R3 and R4 is hydrogen and the other is a hydrocarbon group; and R5 and R6 are each independently hydrogen or a hydrocarbon group], characterized by reacting an N-acylhydrazone represented by the general formula [1]:
[wherein R0 and R2 are as defined above] with an allylating agent such as allyltrichlorosilane or crotyltrichlorosilane in the presence of a chiral phosphine oxide.