3- Chloro-1,1-cyclobutanedicarboxylic

CHLORO-,51, 73 1,1-Cyclobutanedicarboxylic acid, with sulfuryl chloride to give 3-chloro-1,1-cyclobutanedicarboxylic acid, 51,73... 

Cyclobutanedicarboxylic acid has been prepared by hydrolysis of the ethyl ester,1 or of the half nitrile, 1-cyano-l-car-boxycyclobutane.2 The ethyl ester has been prepared by condensation of ethyl malonate with trimethylene bromide1 or chloro-bromide.3 The half nitrile has been prepared by condensation of trimethylene bromide with ethyl cyanoacetate followed by hydrolysis of the ester to the acid.2... 

Sulfonium, cyclopropyldiphenyl tetrafluoroborate, 54, 28 Sulfonium salts, acetylenic, furans from, 53, 3 Sulfonium ylides, 54, 32 Sulfur, reaction with organo-lithium compounds, 50, 105 Sulfuryl chloride, with 1,1-cyclobutanedicarboxylic acid to give 3-chloro-l,1-cyclobutanedicarboxylic acid, 51, 73... 

Chlorocyclobutanecarboxylic acid has been prepared from the rather inaccessible 3-hydroxy-l,l-cyclobutanedicarboxylic acid.4 The related 3-bromocyclobutanecarboxylic acid has also been prepared by a long synthetic scheme of eight steps.5 The present method, based upon the procedure of Nevill, Frank, and Trepka,6 affords the 3-chloro acid in high yield in one step. Thus this method provides a compound which cannot be easily made by other methods. 

Ramberg-Backlund rearrangement. This base was used in the preparation of bicyclo[2.1.1 ]hexene (2) by Ramberg-Backlund rearrangement of the a-chloro sulfone (1), available from 1,3-cyclobutanedicarboxylic acid (several steps). ... 

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