Regio- and Stereoselectivity of Diethylaluminum Azide Opening of Trisubstituted Epoxides and Conversion of the 3° Azidohydrin Adducts to Isoprenoid Aziridines
作者:Chad E. Davis、Jessica L. Bailey、Jonathan W. Lockner、Robert M. Coates
DOI:10.1021/jo026506c
日期:2003.1.1
3-epoxyfarnesol, and 2,3-epoxynerol were formed as single isomers with inversion of configuration at C3 (>or= 35-40:1 for the C(10) azido diols). The regioselectivity was affected by the presence and proximity of oxy functional groups on the epoxide substrate (OH, OAc, and OSi-tBuMe(2)), the equivalents of Et(2)AlN(3), and additives (EtOAc or EtOH). The results and trends are rationalized by consideration
据报道在11种三取代的萜烯环氧化物与Et(2)AlN(3)在甲苯中反应形成的邻位叠氮醇的区域异构体比率(3度,2度/ 2度,3度),在某些情况下是立体化学。根据马尔可夫尼科夫取向和类似S(N)1的过渡态,取代度更高的叠氮化物通常占主导地位(3度,2度/ 2度,3度比率>或= 40:1到2.5-1)。用乙酸6,7-环氧香叶酯(1:2.5)和顺式1,2-环氧li烯(1:3.3至1:10)观察到逆向的区域异构体比率。由2,3-环氧香叶醇,2,3-环氧法尼醇和2,3-环氧神经醇形成的叔叠氮基二醇为单一异构体,其构型在C3处反转(对于C(10)叠氮基,>或= 35-40:1二醇)。区域选择性受到环氧底物(OH,OAc和OSi-tBuMe(2)),Et(2)AlN(3)的当量和添加剂(EtOAc或EtOH)的存在和接近程度的影响。通过考虑拟议的二乙基铝环磷鎓离子中间体和过渡态的结构和立体电子特征,以及