Pauson–Khand reaction

The Pauson–Khand (PK) reaction is a chemical reaction, described as a [2+2+1] cycloaddition. In it, an alkyne, an alkene and carbon monoxide combine into a α,β-cyclopentenone in the presence of a metal-carbonyl catalyst.

Ihsan Ullah Khand (1935–1980) discovered the reaction around 1970, while working as a postdoctoral associate with Peter Ludwig Pauson (1925–2013) at the University of Strathclyde in Glasgow. Pauson and Khand's initial findings were intermolecular in nature, but the reaction has poor selectivity. Most modern applications instead apply the reaction for intramolecular ends.

The traditional catalyst is stoichiometric amounts of dicobalt octacarbonyl, stabilized by a carbon monoxide atmosphere. Catalytic metal quantities, enhanced reactivity and yield, or stereoinduction are all possible with the right chiral auxiliaries, choice of transition metal (Ti, Mo, W, Fe, Co, Ni, Ru, Rh, Ir and Pd), and additives.