The synthesis of 5-hydroxy-2-(β-D-ribofuranosyl)pyridine (12) from 2-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)furan (1) is described. Treatment of 1 with α-methoxycarbamate in the presence of p-toluenesulfonic acid in benzene at reflux temperature afforded furfurylcarbamate (2) and its α-isomer in a 5/1 ratio. The anomerization was circumvented by treatment of 1 with α-methoxycarbamate in the presence
One step synthesis of α-aminoalkylfurans was achieved by the reaction of α-methoxyurethanes or α-methoxyamides with furan. This method was applied to an efficient synthesis of pyridoxine.
Tin tetrachloride-induced π-cyclizations of glycine cation equivalents to substituted pipecolic acid derivatives
作者:Peter M Esch、Ilona M Boska、Henk Hiemstra、Richard F de Boer、W.Nico Speckamp
DOI:10.1016/s0040-4020(01)86443-7
日期:1991.1
Cationic pi-cyclization reactions of N-(3-alkenyl)-N-(methoxycarbonyl)acetoxyglycine esters induced by tin tetrachloride in dichloromethane are described. Reactions started and quenched with water at -78-degrees-C mainly yield cis-4-hydroxypipecolic esters, whereas reactions quenched after warm-up to room temperature provide trans-4-chloropipecolic esters as major products. A mechanistic scheme is advanced which adequately explains these results. The essentials are a rapid cationic aza-Cope equilibrium of the incipient iminium cation, and participation of the ester moiety through formation of a relatively stable bicyclic dioxycarbenium cation as pivotal intermediate.
LASNE, M. -C.;RIPOLL, J. -L.;THUILLIER, A., J. CHEM. RES. SYNOP, 1982, N 8, 214-215
作者:LASNE, M. -C.、RIPOLL, J. -L.、THUILLIER, A.
DOI:——
日期:——
MAEBA, ISAMU;SUZUKI, MAKOTO;TAKAHASHI, NAOKO;IIJIMA, TAKASHI;FURUKAWA, HI+, J. HETEROCYCL. CHEM., 25,(1988) N 2, 503-507