2,2,5,5-Tetra:methyl-cyclopentane-carboxylic acid prepn. - by gas phase rearrangement of 2-iso-cyano-1,1,3,3-tetra-methyl-cyclopentane to the 2-cyano deriv. which is then hydrolysed

摘要

The prepn. of 2,2,5,5-tetramethyl cyclopentane carboxylic acid (I) comprises gas phase rearrangement of 2-isocyano-1,1,3,3-tetramethyl cyclopentane (II) to 2-cyano-1,1,3,3-tetramethylcyclopentane (III) which is then hydrolysed to (I). The rearrangement is at 550-650 (esp. 570-620) deg.C and 10 power (-4) to 30 mbar. USE/ADVANTAGE - (I) can be used in the prepn. of a N-L-aspartyl-N'- (alkylcarbonyl)-1,1-diamino ethane deriv. of formula (IV) which is a water soluble sweetener which has no bitter after taste and is 1000 times sweeter than sucrose. In (IV), R = 2,2,5,5-tetramethylcyclopentane carbonyl (II) can be easily prepd. from 2,2,5,5-tetramethylcyclopentanone. The gas phase rearrangement of (II) to (III) avoids the occurrence of disruptive side reactions. In contrast to known prepns. of (I), no transition metal reagent is necessary, and no protective gas need be used. There are no sepn. problems resulting from the formation of unwanted prods. Yields are considerably better than with previous processes which gave yields of e.g. less than 11%.