HIGH-PRESSURE ORGANIC-CHEMISTRY .19. HIGH-PRESSURE-PROMOTED, SILICA GEL-CATALYZED REACTION OF EPOXIDES WITH NITROGEN-HETEROCYCLES

The reaction of epoxides with nitrogen heterocycles such as indoles, p yrroles, imidazoles, and pyrazoles was studied under both high-pressur e and silica gel-catalyzed conditions. Whereas it has been reported th at the treatment of indole with styrene aside at in kbar and 42 degree s C for 24 h gave 2-(3-indolyl)-2-phenylethanol in 56% yield, the same compound was obtained in 88% yield when the reaction was conducted on silica gel at rt for 1 week. Similarly, efficient reaction of epoxide s with pyrroles, imidazoles, and pyrazoles was achieved. In terms of s tereochemical features, the epoxide ring opening reaction of (R)-(+)-s tyrene oxide with indole was found to proceed stereoselectively in an S(N)2 fashion at the benzyl carbon, in either ease.