M. Yus, Rosa Ortiz, F. Huerta
Oct 20, 2003
Citations
0
Influential Citations
23
Citations
Journal
Tetrahedron
Abstract
Abstract The reaction of 6-chlorohex-1-ene 1 with lithium powder and a catalytic amount of 4,4′-di- tert -butylbiphenyl (DTBB, 5% molar) in THF at −78°C gives the corresponding organolithium intermediate 2 , which by reaction with different electrophiles affords, after hydrolysis with diluted hydrochloric acid, the expected products 3 . The same reaction performed at −30°C gives cyclopentyl derivatives 5 , probably by cyclisation of the open-chain intermediate 2 to give the cyclic organolithium compound 4 . When the double bond in the starting material contains an alkyl substituent, for instance compounds 6 and 9 , the corresponding cyclisation is inhibited, so the corresponding acyclic products 8 and 11 are respectively, obtained. However, when the substituent at the same positions is a phenyl group, like in starting materials 12 and 15 , the cyclised products 14 and 17 were respectively, isolated. In the case of the secondary starting chlorinated material 18 , the reaction can be directed to both, the acyclic products 20 or the cyclic ones 22 , working at −78 or −30°C, respectively, as it happens in the case of the unsubstituted chlorinated material 1 . For the tertiary chloro derivative 23 , only the cyclic compound 27 could be isolated at −30°C due to the great instability of the corresponding tertiary organolithium intermediate 24 , which undergoes a proton abstraction even at −78°C. From allyl 2-chlorophenyl ether 28 or N , N -diallyl-2-chloroaniline 32 , only the corresponding cyclic compounds 31 and 33 , respectively, are isolated either at −78 or at −30°C. In all cases a carbanionic cyclisation, better than a radical one, is postulated to occur as mechanistic pathway.