Pd(II)-Catalyzed Enantioselective Ring-Contraction for the Construction of 1,4-Benzoxazines
2021
Ye, Chenghao | Gao, Feng | Wei, Haipeng | Chen, Jianzhong | Yang, Guoqiang | Yuan, Qianjia | Zhang, Wanbin
Enantioselective ring-contraction reactions have not been widely reported. We have developed an enantioselective ring contraction of 5,6-dihydro-2H-benzo[b][1,4]oxazocines, affording enantiomerically enriched 3,4-dihydro-2H-1,4-benzoxazine derivatives as single regioisomers. An acidic additive is necessary in order to obtain the products with good yields and enantiomeric ratios (up to 93% yield, 98:2 er). The reaction was successfully performed on a gram scale, and the products can be derivatized easily.
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