Kuhn-Winterstein reduction

What is Kuhn-Winterstein reduction?

The Kuhn-Winterstein reduction, which involves the conversion of adjacent diols into corresponding olefins using diphosphorus tetraiodide P2I4, was first reported in 1928. This reaction can be performed on diols that have a terminal acetylene group, as long as the experimental conditions are carefully controlled.

Kuhn-Winterstein reduction - general reaction scheme - diphosphorus tetraiodide P2I4
Kuhn-Winterstein reduction

These conditions include adding the diol to anhydrous pyridine and using a supersaturated solution of diphosphorus tetraiodide P2I4 in carbon disulfide CS2. Typically, this reaction produces trans-olefins as the primary product, unless the diol is part of a ring.

Preparation of diphosphorus tetraiodide P2I4

One way to produce diphosphorus tetraiodide P2I4 is through the disproportionation of phosphorus triiodide in dry ether:

2 PI3 → P2I4 + I2

Another method is by treating phosphorus trichloride PIand potassium iodide KI under anhydrous conditions.