Pd-Catalyzed [4 + 2] cycloaddition of methylene cyclic carbamates with dihydropyrazolone-derived alkenes: synthesis
Biming Mao1,2, Jiaqing Xu1, Wangyu Shi1
1Department of Chemistry and Innovation Center of Pesticide Research, China Agricultural University, Beijing 100193, P. R. China. hchguo@cau.edu.cn.
Abstract:
In this paper, a palladium-catalyzed [4 + 2] cycloaddition of 5-methylene-1,3-oxazinan-2-ones with 4-arylidene-2,4-dihydro-3H-pyrazol-3-ones has been developed to produce spiropyrazolones in high yields with excellent diastereoselectivities in nearly all cases. The cycloaddition reaction was scaled-up without significant loss of yield, and its synthetic utility has been demonstrated by further transformations of the products. The reaction type of N-Ts cyclic carbamates under palladium catalysis was extended to include [4 + 2] cycloaddition for the first time.
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