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Nucleophilic Cyclization of o ‐Alkynylbenzamides Promoted by Iron(III) Chloride and Diorganyl Dichalcogenides: Synthesis of 4‐Organochalcogenyl‐1 H ‐isochromen‐1‐imines
Author(s) -
Neto Jose S. S.,
Back Davi F.,
Zeni Gilson
Publication year - 2015
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201403534
Subject(s) - chemistry , nucleophile , electrophile , moiety , sonogashira coupling , imine , medicinal chemistry , regioselectivity , triple bond , combinatorial chemistry , polymer chemistry , organic chemistry , catalysis , double bond , palladium
We have developed a method for the preparation 4‐organochalcogenyl‐1 H ‐isochromen‐1‐imines from o ‐alkynylbenzamides. This electrophile‐promoted nucleophilic cyclization achieved by treatment with a combination of iron salts and diorganyl dichalcogenides. FeCl 3 and diorganyl dichalcogenides reacted with o ‐alkynylbenzamides under aerobic conditions at room temperature and in the absence of additives to give 4‐organochalcogenyl‐1 H ‐isochromen‐1‐imines in good yields and with good selectivities. The reaction took place with 0.5 equiv. of the diorganyl dichalcogenides, which demonstrates that both halves of the diorganyl dichalcogenides (RYYR → 2RY) were incorporated into the final product. Mechanistic studies suggested that the regioselectivity of the cyclization is governed by a seleniranium ion, a key intermediate formed by the electrophilic addition of the organochalcogen moiety to the carbon–carbon triple bond. The utility of the 4‐organochalcogenyl‐1 H ‐isochromen‐1‐imines was also demonstrated by their application as starting materials in Suzuki and Sonogashira cross‐coupling reactions.