Chapter 12, Problem 12.25P

Interpretation Introduction

Interpretation:

The structures of the initial alkyne A and intermediate B in the reaction of A with disiamylborane, followed by a basic solution of ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$ to produce the given aldehyde are to be drawn.

Concept introduction:

Disiamylborane (${{\text{(C}}_{\text{5}}{\text{H}}_{\text{11}}\text{)}}_2\text{BH}$) reacts specifically with terminal alkynes to produce an Anti-Markovnikov addition product. Only one molecule of disiamylborane adds to the alkyne because of the bulky alkyl groups attached to the boron atom. Oxidation of this addition product under the basic condition leads to the formation of an enol, which tautomerizes to an aldehyde under the reaction conditions.