Dichloro-2,2-difluoroethene

In the [2 + 2] cycloadditions of 10 with iV-phenylmaleimide and dimethyl fumarate, the major cycloadducts were formed with a very high degree of ee transfer from 1,3-dimethylallene8. Similar results were obtained in the reaction of 10 with 1,1-dichloro-2,2-difluoroethene. The reaction with less reactive 1,1-diphenylethene did not lead to cycloadduct formation, but resulted in racemization of the chiral 1,3-dimethylallene instead9, which implies reversible formation of the diradical intermediate in this case. Finally, the cycloaddition of 1,3-dimethylallene to methyl propiolate (14) afforded two cycloadducts, 15 and 16, to which >40% of the initial ee had been transferred (equation 5)11. 

The reactions of l-t-butyl-3-methylallene with several alkenes, e.g. IV-phenylmalei-mide, acrylonitrile and methyl acrylate, afforded exclusively [4 + 2] cycloadducts of 1-t-butyl-l,3-butadiene, which had been formed from l-t-butyl-3-methylallene by a [1,3] sigmatropic rearrangement12. The reaction of l-t-butyl-3-methylallene with 1,1-dichloro-2,2-difluoroethene occurred more rapidly than the hydrogen shift, which allowed the... 

The thermal cyclodimerization of fluoroalkenes represents a route to fluorinated cyclobutanes. In most cases the neat alkene is heated in a sealed tube for prolonged periods of time. For symmetrical fluoroethenes head-to-head dimerization predominates. For instance, 1.1-dichloro-2,2-difluoroethene (1) undergoes thermal dimerization (180°C, 14 days) to give the hcad-to-hcad dimer 2 although no yield was reported.1... 

A stainless steel autoclave was charged with 1,1 -dichloro-2,2-difluoroethene (3 400 g, 3 mol), then agitated at 200 C. After 12 h the autoclave was cooled to rt and unreacted monomer (75 g bp 19 C) was recovered by distillation. The residue was dissolved in Et20, then distilled to give 4 yield 313 g (96% based on conversion) bp 131-132 C. 

Organometallic Derivatives of Monocyclic Thiophens - Lithium. Numerous a-substituted thiophens have been prepared via metallation of thiophens with organolithium derivatives. Thus 2-thienyl-lithium has been allowed to react with tetraisopropylthiuram disulphide to give 5-(2-thienyl) A(,A -di-isopropyl-dithiocarbamate in quantitative yield. ° Through the reaction of 2-thienyl-lithium with tellurium in THF, the tellurolate was obtained, which was converted into various products. The reaction of 2-thienyl-lithium with 1,1-dichloro-2,2-difluoroethene has been developed into a very useful method for... 

Scheme 37. Thus simple methods are available for alkylation of / -quinones [39] and maleic anhydride [29], whilst, inter alia, hydrolysis of the adducts from 1,1-dichloro-2,2-difluoroethene with aqueous silver nitrate THF provides homologated a,a-difluoroalkane-carboxylic acids [40].

Scheme 6.49. A representation of the radicals that might be involved in the reaction of 1,1-dichloro-2,2-difluoroethene with ( )- ,3-pentadiene. The justification (in part) for suggesting that the reaction involves radicals is the observation that the product is 2,2-dichloro-l,l-difluoro-3-[l-(i )-propenyl]cyclobutane rather than the isomeric l,l-dichlor-2,2-difluoro-3-[ -( ) -propenyl] cyclobutane.

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