SäurekatalysierteUmlagerung von 4-Allyl-cyclohex-2-en-1-olen; Beispielefürladungskontrollierte [3 s,4 s ] -Umlagerungen von cyclischen Allylkationen
摘要:
的酸催化的重排的环己-2-烯-1-醇15,d 3 - 15,16,17和19中,环己-2,5-二烯-1-醇20和21,并且还烯丙基醇在室温下使用98%的硫酸/乙酸酐(1:99)研究了图22和23(方案3)。通过4-烯丙基-4-苯基-环己-2-烯-1-醇的重排(15),反应时间大于2小时,可以得到单一产物4-烯丙基-联苯(50),产率为33% (方案9)。低于2小时乙酸反应时间53从隔离了15个,可以将其转换为50个。2',3',3'-d 3 -15在Ac 2 O / H 2 SO 4中的反应导致1',1',2'-d 3 -50(方案11)。4-烯丙基-4-甲基-环己-2-烯-1-醇的重排(16)(方案14)产生39%的相应乙酸盐60和30%的4-烯丙基-甲苯(6)结果是在反应条件下重排60。这些重排均为[3s,4s]-σ反应,其通过环己烯基阳离子a进行(方案12,R = C 6 H 5,CH
A New Synthesis of Pyrrolidines by Way of an Enantioselective Mannich/Diastereoselective Hydroamination Reaction Sequence
摘要:
A new two-step synthesis of highly substituted pyrrolidines has been developed. Chiral silane Lewis acid promoted enantioselective Mannich reactions of silyl ketene imines with acylhydrazones may be used to access bishomoallylic benzoic hydrazides that In turn may be cyclized to pyrrolidines by way of the thermal hydroamination reaction reported recently by Beauchemin. Importantly, excellent diastereoselectivity may be realized in the hydroamination reactions.