Mercuracarborand-catalyzed Diels-Alder reactions of a thionoester with cyclopentadiene
摘要:
The multidentate Lewis acids B-octamethyl [12]-mercuracarborand-4 (1) and B-hexamethyl [9]-mercuracarborand-3 (2) catalyze the Diels-Alder reaction of a thionoester 4 with cyclopentadiene. The reaction proceeds more rapidly when catalyzed with 1 and 2 than with monodentate bis(closo-9,12-dimethyl-1,2-carboran-1-yl)mercury (3). Mercury-199 NMR studies demonstrated the formation of a 1:1 complex of 1 with 4 in which the thio function of 4 is coordinated to the HE(II) centers of 1, while the 2.4 and 3.4 complexes are not observed by NMR. (C) 1999 Elsevier Science Ltd. All rights reserved.