Asymmetric synthesis of (R)-hexane-1,5-diol, (R)-hex-3-ene-1,5-diol and (R)-6-methylhept-5-en-2-ol (sulcatol) employing a tandem asymmetric conjugate addition and stereospecific Meisenheimer rearrangement protocol
作者:Stephen G. Davies、G. Darren Smyth
DOI:10.1039/p19960002467
日期:——
Highly stereoselective conjugate addition of lithium (R)-N-methyl-(α-methylbenzyl)amide to tert-butyl (E,E)-hexa-2,4-dienoate, followed by reduction of the ester to the corresponding alcohol, affords a substrate which undergoes, upon oxidation, a stereospecific Meisenheimer rearrangement to give a single diastereomer of the corresponding trialkylhydroxylamine. The analogous N-benzyl adduct gives lower
将(R)-N-甲基-(α-甲基苄基)氨基锂高度立体选择性共轭加成到(E,E)-六-2,4-二烯酸叔丁酯中,然后将酯还原成相应的醇,得到底物在氧化时经历立体定向的迈森海默重排,得到相应的三烷基羟胺的单一非对映异构体。类似的N-苄基加合物在氧化重排反应中的收率较低。如果酯不还原为醇,则N-氧化导致Cope消除,而不是Meisenheimer重排。N–O键的裂解给出(R)-己-3-烯-1,5-二醇和双键的氢化得到高ee的(R)-己烷-1,5-二醇。这种方法已被应用到的昆虫信息素的合成(- [R从)-6-甲基庚-5-烯-2-醇(sulcatol)叔丁基(ê,ê) -六-2,4-二烯酸酯,经由一个该序列涉及酰胺锂的共轭加成,酯的格利雅(Grignard)加成,迈森海默重排,双键加氢,叔醇脱水以及最后的N-O键断裂。