2.4.1 Tributyltin Hydride (Bu3SnH)

Tributyltin hydride (TBTH) is an organotin compound can acts as a reducing agent when treated with a radical initiator such as azobisisobutyronitrile (AIBN) or by photo irradiation. It is a coluorless liquid and is generally purified by distillation.

T. V. Rajanbabu, Encyclopedia of Reagents for Organic Synthesis, John Wiley and Sons, Inc., L. A. Paquette, Ed., New York, 1995, 7, 5016.

2.4.1.1 Reductive Dehalogenation

The halogens are removed by TBTH in presence of AIBN in aromatic hydrocarbon solvent such as benzene, toluene. The AIBN acts as a radical initiator and needed in catalytic amount (2-5 mol %). The reactivity order of the halogens is I > Br > Cl and F does not work under these conditions (Scheme 1-2).

Scheme 1

Scheme 2

2.4.1.2 Radical Cyclization

The radical cyclization of the suitably substituted halides could be performed in presence of TBTH to give the desired cyclized products (Scheme 3). The reaction undergoes via radical pathway.

Scheme 3