reaction with aldehydes leads to diastereomeric aldols 4 and 5. Acetylation followed by acetic acid elimination of the aldols provides a stereoselective and high yield route to 2-alkylidene-3,4-dihydro-3-oxo-2H-1,4-benzothiazines.
4-甲基-3,4-二氢-3-氧代--2H-1,4-苯并
噻嗪与
LDA的
金属化以及随后与醛的反应导致生成非对映异构醇醛4和5。乙酰化,然后消除醛醇的
乙酸为2-亚烷基-3,4-二氢-3-氧代-2H-1,4-苯并
噻嗪提供了立体选择性和高产率的途径。