Treatment of 2-(4-methoxyphenyl)-4, 4a, 5, 6-tetrahydro-(1)benzothiepino[5, 4-c]pyridazin-3(2H)-one 7-oxide (1a) in methanesulfonic acid (MSA) gave 2-(4-methoxyphenyl)-5, 6-dihydro-(1)benzothiepino[5, 4-c]pyridazin-3(2H)-one (2a) in 80% yield. Compound 2a was also obtained by reating 4a, a deoxidized compound of 1a, with dimethylsulfoxide (DMSO) in MSA, trifluoroacetic acid or HBr-AcOH. Apparently this novel dehydrogenation reaction was derived from an acid catalyzed intermolecular redox reaction, that is, a concerted elimination of 4-hydrogen, 4a-hydrogen on 1a or 4a and sulfinyl oxygen on 1a or DMSO.
在
甲磺酸(M
SA)中处理 2-(4-
甲氧基苯基)-4, 4a, 5, 6-四氢-(1)
苯并噻吩并[5, 4-c]
哒嗪-3(2H)-酮 7-氧化物(1a),可得到 2-(4-
甲氧基苯基)-5, 6-二氢-(1)
苯并噻吩并[5, 4-c]
哒嗪-3(2H)-酮(2a),收率为 80%。将 1a 的脱氧化合物 4a 与
二甲基亚砜 (
DMSO) 在 M
SA、
三氟乙酸或 HBr-AcOH 中进行再反应,也可以得到化合物 2a。显然,这种新型脱氢反应是由酸催化的分子间氧化还原反应产生的,即 1a 或 4a 上的 4-氢、4a-氢和 1a 或
DMSO 上的亚
硫酰氧协同消除。