Diborane as a Reducing Agent. Part III. The Reduction of Oxygen Heterocyclic Carbonyl Compounds and Aromatic Esters, and the Catalytic Action of Boron Trifluoride

Abstract

Diborane reduction of benzpyrones and coumarins results in both hydrogenolysis of the carbonyl function and cleavage of the heterocyclic ring. Coumarin itself afforded o-allylphenol, but more complex products were obtained from a substituted coumarin, and from chromone and flavone.

The relative inertness of aromatic esters towards diborane has also been investigated, and a possible explanation is advanced. In the diborane reduction of certain aromatic aldehydes and ketones it has now been confirmed that traces of boron trifluoride can exercise a catalytic action in promoting hydrogenolysis of the oxygen function. The instability of diborane solutions in ethereal solvents may also be due to traces of boron trifluoride.