Novel Betaines of the Hexaalkylguanidinio-carboxylate Type

Matthias Walter and Gerhard Maas Institute for Organic Chemistry I, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany Reprint requests to Prof. Dr. Gerhard Maas. Fax: 49 (0)731-5022803. E-mail: [email protected] Z. Naturforsch. 2009, 64b, 1617 – 1624; received September 29, 2009 Dedicated to Professor Hubert Schmidbaur on the occasion of his 75th birthday Betaines 7a, b and 8a, b have been prepared from 3and 4-piperidinecarboxylic acid and N,N,N′,N′-tetraalkyl-chloroformamidinium chlorides via the corresponding methyl esters. These betaines are highly hygroscopic, thermally very stable, and, with the exception of 7b, have rather low melting points. They undergo a surprisingly facile alkaline cleavage of the hexaalkylguanidinium moiety. They react with dichloromethane by a twofold nucleophilic substitution to form methylene dicarboxylates such as 11. The NMR (1H, 13C) data of betaines 7 and 8 are discussed.