Reduction of epoxide

Question

Does $\ce{LiAlH4}$ and $\ce{NaBH4}$ reduce an isolated epoxide? I have two books where both are saying differently. One says it can and other says cannot. On searching the web there was no definite answer. Can they reduce epoxide to diol or something else ?

I am aware of the reduction of the other groups in the picture:

Sources: NCERT: yes; JEE Advanced 2016 paper solution by Arihant: no; multiple coaching stuff: both yes/no

Answer 1

The correct question (taken from the 2016 JEE Paper is):

Lithium Aluminium Hydride reduces epoxides¹, hence (A) would not give the required product. LAH also reduces ethers to primary alcohols, which is an easier way of eliminating the option (A). $\ce{BH3}$ in THF can reduce the acid, as explained in this question, hence the requisite product would not be obtained.

$\ce{NaBH4}$ cannot reduce esters, acids or epoxides in the absence of catalysts such as $\ce{PdCl2}$ or $\ce{AlCl3}$ and diglyme, hence (C) would be a correct option here.

Can you tell what Raney Ni would do here?

Raney Ni Reduces carboxylic acid and esters at elevated temperature (eg: $\pu{350 K}$); and no reaction with epoxide. So, it can be used for selective reduction of aldehyde at room temperature ($\pu{298 K}$).

Use this resource to help yourself out and as a reference for such reactions in the future.

References:

1. Murphy, David K., et al. “Reduction of Epoxides. III. Lithium Aluminum Hydride and Mixed Hydride Reduction of Some Secondary-Tertiary Epoxides.” Journal of the American Chemical Society, vol. 91, no. 10, May 1969, pp. 2649–53. doi:10.1021/ja01038a042.