Synthesis 2019; 51(10): 2136-2148
DOI: 10.1055/s-0037-1610691
paper
© Georg Thieme Verlag Stuttgart · New York

Base-Mediated Tandem 1,6-Addition/Cyclization/Isomerization Reactions between para-Quinone Methides and Benzyl Chlorides: Approaches to Diverse Frameworks at Each Cascade Stage

Shangkun Zhao
a   College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, P. R. of China   Email: xixisong@zzu.edu.cn
,
Yuanyuan Zhu
a   College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, P. R. of China   Email: xixisong@zzu.edu.cn
,
Minli Zhang
a   College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, P. R. of China   Email: xixisong@zzu.edu.cn
,
Xixi Song*
a   College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, P. R. of China   Email: xixisong@zzu.edu.cn
,
Junbiao Chang*
a   College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, P. R. of China   Email: xixisong@zzu.edu.cn
b   Collaborative Innovation Center of New Drug Research and Safety Evaluation, Henan Province, Zhengzhou 450001, P. R. of China   Email: changjunbiao@zzu.edu.cn
› Author Affiliations
We are grateful to the NSFC (#21302173) and the Education Department of Henan Province (#19A150049) for financial support.
Further Information

Publication History

Received: 13 November 2018

Accepted after revision: 08 January 2019

Publication Date:
19 February 2019 (online)


Abstract

Base-mediated stereospecific tandem reactions using para-quinone methides and carbene-like benzyl chlorides are developed. DBU-mediated 1,6-addition/cyclization/isomerization reactions produce triarylsubstituted alkenes in 43–89% yields and Z/E ratios of 5:1 to 35:1 in favor of the Z-isomers. Single-step 1,6-conjugate additions are realized with the mediation of cesium carbonate, and different triaryl chloroethanes are obtained in yields of 41–54% and excellent diastereoselectivities of more than 20:1. In addition, tandem 1,6-addition/cyclization reactions are achieved using tuned 2,4-disubstituted benzyl chlorides to afford diaryl spirocyclopropyl para-dienones in yields of 35–83% and diastereoselectivities of more than 20:1 in favor of the anti-isomers. The transformations from triaryl chloroethanes and spirocyclopropyl para-dienones into triarylsubstituted alkenes are also demonstrated to support the proposed tandem mechanisms.

Supporting Information