Endohedral metal-induced regioselective formation of bis-prato adduct of Y3N@ Ih-C80 and Gd3N@ Ih-C80

Abstract

Regioselective bisaddition of M3N@Ih-C80 (M = Y, Gd) was observed for the first time in the Prato reaction with N-ethylglycine and formaldehyde. The main kinetic bisadduct of Y3N@C80 was determined to be a [6,6],[6,6] adduct by 1H and 13C NMR and vis/NIR spectroscopy, and it converted to a mixture of regioisomers upon heating via a sigmatropic rearrangement. The main kinetic bisadduct of Gd3N@C80 (the [6,6],[6,6] adduct on the basis of vis/NIR data) existed stably under thermal conditions without isomerization. The likely position of the second addition of the Gd3N@C80 bisadduct was predicted by DFT calculation

This research was supported in part by the Swiss National Foundation (200021-140451 and 200021-156097 to Y.Y.), ETHZ (Grant ETH-25 11-1 to Y.Y.), JST PRESTO (to Y.Y.), the American Heart Association (SDG 0930140N to Y.Y.), the Spanish MECD (Ph.D. Fellowship AP2010-2517 to M.G.-B.), Spanish MINECO (Projects CTQ2011-23156/BQU and CTQ2011-25086/BQU and Juan de la Cierva Postdoctoral Grant JCI-2012-14438 to S.O.), and the European Community (CIG Project PCIG14-GA-2013-630978 to S.O.)