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This is a problem of IChO-2014(&solution).But I am having trouble working out reaction mechanism of the second reaction or even how the product B formed. This reaction is somewhat new to me. And googling didn't help much.

Just need a little hint on this regard.

  • $\begingroup$ And Googling didn't seem much help. $\endgroup$ Feb 23, 2017 at 0:50
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    $\begingroup$ The key also for the second reaction is the use of a very bulky borane. There are two sites for hydroboration, and we are selecting for the one that is less hindered. Using a hindered borane at low temperature means that we can avoid reacting much at the tri-substituted double bond. Too bad it also takes seven days to react at the less substituted double bond. $\endgroup$
    – Zhe
    Feb 23, 2017 at 15:27
  • $\begingroup$ @Zhe What does acetone do in forming B to C? $\endgroup$ Feb 24, 2017 at 12:42
  • $\begingroup$ As usual, below the arrow, it's solvent. $\endgroup$
    – Zhe
    Feb 24, 2017 at 13:54

1 Answer 1


A to B is a classic hydroboration of the least hindered double bond followed by oxidation of the trialkyl borane.


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