# Regioselective Transfer Hydrogenation of Substituted Oxiranes with Alcohols Using MgO as the Catalyst

## TL;DR

This study demonstrates high regioselectivity in hydrogenating various oxiranes using magnesium oxide as a catalyst in the vapor phase.

## Contribution

The study introduces MgO as an effective catalyst for vapor-phase CTH of substituted oxiranes with high regioselectivity.

## Key findings

- Primary alcohols were the main products with high regioselectivity (93-100%) for methyl-, n-butyl-, and phenyloxirane.
- Vapor-phase CTH of methyloxirane with 2-pentanol produced three products with yields of 48%, 4%, and 35%.
- Phenyloxirane CTH yielded 95% 2-phenylethanol with minor byproducts.

## Abstract

An excellent regioselectivity of vapor-phase catalytic transfer hydrogenation (CTH) of substituted oxiranes (methyl-, n-butyl-, and phenyloxirane) with alkanols (EtOH, 2-PrOH or 2-PeOH) as hydrogen donors in the presence of magnesium oxide as a catalyst was attained. In the vapor phase, all of these oxiranes as well as 1,2-epoxycyclohexane were hydrogenated. Moreover, it was found that primary alcohols were always the main products of CTH of methyl-, n-butyl-, and phenyloxirane with very good regioselectivity towards the alcohols: 93, 73, and 100%, respectively. It was shown that vapor-phase CTH of methyloxirane with 2-pentanol led to three products, two regioisomeric propanols, (1-PrOH and 2-PrOH), and also 1-(2-pentyloxy)-2-propanol. Their yields were 48%, 4%, and 35%, respectively. Two regioisomeric hexanols (1-HeOH, 54% yield and 2-HeOH, 20% yield) and 2-hexanone (14% yield) were found as products of the CTH of n-butyloxirane with 2-propanol as the hydrogen donor. For vapor-phase CTH of phenyloxirane, only 2-phenylethanol (95% yield) was observed together with minor amounts of phenylacetaldehyde. In vapor-phase CTH of 1,2-epoxycyclohexane, the presence of the transfer hydrogenation products (2-cyclohexenone, cyclohexanol, and cyclopentylmethanol) as well as isomerization products (cyclohexanone, 2-cyclohexenol, and 3-cyclohexenol) were found. It was noted that at 623 K, the yields of the former products were 18, 22, and 14%, respectively. Liquid-phase CTH of n-butyl- or phenyloxirane with 2-pentanol (b.p. 392 K) was unsuccessful.