Reduction of epoxides. III. Lithium aluminum hydride and mixed hydride reduction of some secondary-tertiary epoxides

Development of Dirhodium(II)-Catalyzed Generation and Enantioselective 1,3-Dipolar Cycloaddition of Carbonyl Ylides

“…Epoxide opening of substituted 1,2‐epoxycyclohexanes is well documented in the literature 8. In general, a trans ‐diaxial stereoselectivity is found, as dictated by stereoelectronic effects 9–13. However, the observed regioselectivity depends largely on conformational bias and can be modulated by a judicious choice of reaction conditions.…”

“…It seems thus reasonable to assume that the major conformers in solution are the equatorial ones ( E1 and E2 , Scheme ) and that most of the Li ion is coordinated with the solvent 19. The major or exclusive formation of C1 regioadducts can thus be explained either by operation of the postulated “ trans ‐diaxial” opening from a low populated reactive conformation A1 or by an alternative, formal “ trans ‐diequatorial opening” from any of the equatorial conformers, in clear conflict with the accepted stereoelectronic control for these processes 9–13…”

Synthesis of a Phenanthridine Analogue of Natural Isocarbostyril Alkaloids

“…28 This reaction takes place through an S N 2 mechanism, providing, mainly, a diol with diaxial configuration. 28,29 The relative configuration of compound 4 was determined by using the values of the coupling constants between the hydrogen atoms. The coupling constants J 3,4 , J 4,5 , and J 5,6a presented values of 11.0, 11.0, and 12.0 Hz, respectively, typical of a trans diaxial arrangement ( Figure 5).…”

Reduction of Epoxides

“…o MeOH/ButOH 18% Phy OH (14) Because of the low reactivity of sodium borohydride, functional groups such as carbamonyl, carbonyl, nitro and cyano groups, which are generally reduced with LAH, can tolerate the reaction conditions. 28 For example, it has been used for the selective reduction of an epoxy group in an w-cyano epoxide (equation 15).29 CN MeOH/ButOH OH CN (15) 2-Phenylpropene oxide is selectively reduced in the presence of trans-stilbene oxide even with an excess amount of sodium borohydride (equation 16),28 and a similar system using lithium borohydride (LiBH4) also shows selective reduction of a styrene oxide in the presence of a benzamide.…”