Triphenylphosphine dichloromethylene

The nucleophilic character of triphenylphosphine and the electrophilic character of carbenes suggested to two groups of investigators that the two reagents should combine to form ylides of a new type to use in expansion of the Wittig reaction. Speziale et ai. found that triphenylphosphine on treatment in pentane with chloroform and potassium t-butoxide at 0° gives yellow triphenylphosphine dichloromethylene, which reacts with benzophenone to yield I,l-diphenyl-2,2-dichloroethylene (1). 

Lakhrissi, M, Chapleur, Y, Dichloromethylenation of lactones 6 efficient synthesis of dichloroolefins from lactones and acetates using triphenylphosphine and tetrachloromethane, J. Org. Chem., 59, 5752-5755, 1994. 

Dibenzo (18) crown-6 64 Dicarbonyi ba(triphenylphosphine)mckel 390 Dichlorodieyanoquinone (DDQ) 285 Dichloromethylene dlmethylammonium chloride (Viehe reagent) 399 Oichloromethytphosphme 247... 

The reaction of perchlorotoluene with triphenylphosphine has been studied (Diaz-Alzamora, 1968). It is noted that the reaction with carbon tetrachloride gives a mixture of (dichloromethylene)triphenylphosphorane and triphenylphosphine dichloride (Appel et al., 1976 Burn and Cadogan, 1963 Rabinowitz and Marcus, 1962). (The resulting reaction mixture was usually treated with water.) The sequence (49), involving a nucleophilic attack on chlorine, has been proposed. 

Triphenyl(trichloromethyl)phosphonium chloride and (dichloromethylene)tri-phenylphosphorane are important intermediates in the reaction system triphenyl-phosphine/carbon tetrachloride. Solutions of (dichloromethylene)triphenyl-phosphorane, which is a convenient Wittig reagent, were first prepared by the addition of dichlorocarbene to triphenylphosphine in chloroform. However, the ylide could not be separated without degradation caused by the reaction medium. 

The transformation of aldonolactones into the corresponding dichloromethylene derivatives on reaction with triphenylphosphine-carbon tetrachloride reagent has been described (Scheme 10). This reagent is of more general applicability than the bis(dimethylamino)phosphine-carbon tetrachloride reported earlier (Vol. 18, p.34). Ester carbonyl groups are also dichloromethylated. 

Dichloroalkenes and Vinyl Chlorides. The reaction of aldehydes produces a mixture of the 1,1-dichloroalkene and the dichloromethylene derivatives. These are the result of reaction of the in situ generated Dichloromethylenetriphenylphosphorane and Triphenylphosphine Dichloride, respectively. Benzaldehyde (eq 32) produces a 1 1 mixture of the dichloroalkene and benzal chloride in 72% yield. ... 

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