Hetero Diels-Alder Reactions of 2-Chloro-1nitroso-1-phenylethene: Preparation of Novel 4-Chloro-Substituted 1,2-Oxazins and Subsequent Reactions
作者:Reinhold Zimmer、Jörg Angermann、Ute Hain、Florian Hiller、Hans-Ulrich Reissig
DOI:10.1055/s-1997-1373
日期:1997.12
The cycloaddition of 2-chloro-1-nitroso-1-phenylethene (3), generated in situ from 2,2-dichloro-1-phenylethan-1-one oxime (2) to electron-rich olefins, e.g. silyl enol ethers or alkyl enol ethers, furnished the 4-chloro-substituted 5,6-dihydro-4H-1,2-oxazines and 6H-1,2 oxazines in moderate to good yields and with good diastereoselectivities. Bromo enol ether 18 led to the unexpected α,α-dichloro oxime derivative 21 as well as the halogenated 6H-1,2-oxazines 19 and 20. Starting from 4-chloro-1,2-oxazines 5 and 17, 4-azido-, 4-amino-, 4-hydroxy-, and 4-oxo-substituted 1,2-oxazines were prepared. Hydrogenolysis of 5,6-dihydro-4H-1,2-oxazine 5 afforded amine 31.
在电子丰富的烯烃,例如硅醚醇或烷基醚醇存在下,2-氯-1-亚硝基-1-苯乙烯(3),由2,2-二氯-1-苯乙酮肟(2)原位生成,经过环加成反应,以中等到良好的产率和良好的非对映选择性得到4-氯取代的5,6-二氢-4H-1,2-嗪和6H-1,2-嗪。溴醚醇18意外地产生了α,α-二氯肟衍生物21以及卤代的6H-1,2-嗪19和20。以4-氯-1,2-嗪5和17为起始物,合成了4-叠氮基、4-氨基、4-羟基和4-氧代取代的1,2-嗪。氢解5,6-二氢-4H-1,2-嗪5得到了胺31。