McCormack reaction

The McCormack reaction , also known as the McCormack cycloaddition, is a name reaction in organic chemistry . It was named after its discoverer, the chemist William B. McCormack. This reaction is used to synthesize phospholene oxides, i.e. heterocyclic five-membered rings with an oxidized phosphorus atom and a C = C double bond in the ring.

Overview reaction

In this cycloaddition , 1,3-butadiene and dichlorophosphine form a phosphole:

The radical R here stands for an alkyl , alkoxy , aryl or halogen radical .

Reaction mechanism

The following reaction mechanism comes from the book "Comprehensive Organic Name Reactions and Reagents" and is only one possible reaction mechanism:

A dichlorophosphole 2 is formed by a suprafacial ring closure between 1,3-butadiene 1 and dichlorophosphine . The dichlorophosphole 2 forms an equilibrium in which it gives off a chloride anion and becomes a phosphorus cation itself. Treatment with water forms hydrochloric acid and a hydroxyl group on phosphorus 3 . Through an intramolecular reaction, hydrogen chloride is split off and phospholene oxide 4 is formed .

“Alternatives” to 1,3-butadiene

In addition, various radicals can be bonded in position 2,3 of the 1,3-butadiene. Several realized examples are presented in the Wang, e. B. starting from 1,2-dimethylene cyclohexane. WB McCormack showed that isoprene can also serve as a starting material instead of 1,3-butadiene .

Individual evidence

↑ Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , p. 1679.
↑ Patent US2663737 : Substituted phosphacyclopentene oxides and process of preparing them. Registered on August 7, 1951 , published December 22, 1953 , inventor: WB McCormack. ‌
↑ ^a ^b Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , p. 1680.
↑ Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , pp. 1680-1681.
^ WB McCormack: 3-Methyl-1-Phenylphospholene oxide In: Organic Syntheses . 43, 1963, p. 73, doi : 10.15227 / orgsyn.043.0073 ; Coll. Vol. 5, 1973, p. 787 ( PDF ).

[Wang_1477-1] Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , p. 1679.

[McCormack_2-2] Patent US2663737 : Substituted phosphacyclopentene oxides and process of preparing them. Registered on August 7, 1951 , published December 22, 1953 , inventor: WB McCormack. ‌

[Wang_21-3] Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , p. 1680.

[Wang_1-4] Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 2 Volume Set . John Wiley & Sons, Hoboken, NJ 2009, ISBN 978-0-470-28663-0 , pp. 1680-1681.

[McCormack-5] WB McCormack: 3-Methyl-1-Phenylphospholene oxide In: Organic Syntheses . 43, 1963, p. 73, doi : 10.15227 / orgsyn.043.0073 ; Coll. Vol. 5, 1973, p. 787 ( PDF ).