... Syntex Research, Institute of Organic Chemistry, Palo Alto, California 94304 Received April 5, 1990 ... and that hard electrophiles should be preferentially directed thereto (Abronin, I. A,; Belenkii, L. I.; Col'dfarb, YL New Trends in Heterocyclic Chemistry; Elsevier: Am ... 6318 J. Org. ...