A direct method for the conversion of terminal epoxides into gamma-butanolides.
A new and efficient process for the conversion of terminal epoxides to gamma-butanolides is described involving Lewis acid promoted epoxide ring-opening by 1-morpholino-2-trimethylsilyl acetylene. Addition of a terminal epoxide to a solution of the ynamine and boron trifluoride diethyl etherate in dichloromethane at 0 degrees C rapidly affords a cyclic keteneaminal that can be hydrolyzed and protodesilylated under mild conditions to provide the corresponding gamma-butanolide in high yield. The net transformation is equivalent to an acetate enolate opening of terminal epoxides. The formation of a cyclic keteneaminal as the direct addition product was observed by monitoring of the reaction by IR and NMR spectroscopy. Functionalized gamma-lactones were prepared by the interception of the reactive cyclic keteneaminal prior to hydrolysis. Reactions with enantiomerically enriched terminal epoxides provide the corresponding gamma-butanolides without loss of optical activity. The compatibility of the present methodology with a wide range of functional groups is noteworthy.
Movassaghi
Mohammad
M
Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
Jacobsen
Eric N
EN
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D004852:Epoxy Compounds / Q000737:chemistry*
D004852:Epoxy Compounds; D015107:4-Butyrolactone