In the following reaction:

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According to me we can use HSCH2CH2SH, followed by Raney Ni

But the answer is that we cannot achieve this conversion by that reagents . Why we cannot use them?

  • 5
    $\begingroup$ Thiols can open epoxides, perhaps preferentially to reaction with the ketone $\endgroup$
    – NotEvans.
    Commented Aug 1, 2016 at 17:10
  • 1
    $\begingroup$ As mentioned in comment, under the conditions required to form the dithiane, the thiol will likely open the epoxide and probably cause polymerisation. $\endgroup$
    – user32431
    Commented Aug 1, 2016 at 20:01

1 Answer 1


You could first react the epoxide with HCl to form the halohydrin (reversible), followed by Clemmensen reduction which selectively reduces ketones and aldehydes to alkanes (no effect on the halohydrin), before finally restoring the epoxide by adding base.


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