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Synthesis of Pterocarpans by Means of a “Disfavored” 5‐ endo ‐ trig Radical Cyclization Reaction
Author(s) -
Santhosh Kalpathy Chidambareswaran,
Gopalsamy Ariamala,
Balasubramanian Kalputtu Kuppuswamy
Publication year - 2001
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 - 10.1002/1099-0690(200109)2001:18<3461::aid-ejoc3461>3.0.co;2-9
Subject(s) - chemistry , tributyltin hydride , radical cyclization , aryl , mitsunobu reaction , ether , stereoselectivity , organic chemistry , stereochemistry , catalysis , alkyl
A successful synthesis of pterocarpans 1 , based on a “disfavored” 5‐ endo ‐ trig radical cyclization reaction, has been accomplished. The radical precursor 4‐(2′‐bromoaryloxy)‐2 H ‐chromene 8 was synthesized in six steps, starting from aryl propynyl ether 2 . On treatment with tributyltin hydride in refluxing benzene, aryl enol ether 8 underwent radical cyclization to furnish the pterocarpan 1. A deuterium label study was performed to prove the occurrence of 5‐ endo ‐ trig radical cyclization. This methodology was extended further to synthesize a class of hitherto unknown pterocarpans 13. A novel and stereoselective route towards the synthesis of aryl ethers of bromohydrins by means of the Mitsunobu reaction is also described.