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Total Synthesis of 3‐Oxo‐ and 3β‐Hydroxytauranin via Negishi Coupling of a Bis( ortho ‐oxy)‐Functionalized Benzyl Chloride
Author(s) -
Göhl Matthias,
Seifert Karlheinz
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.201500815
Subject(s) - negishi coupling , chemistry , chloride , yield (engineering) , thionyl chloride , allene , tandem , organic chemistry , combinatorial chemistry , medicinal chemistry , reagent , catalysis , materials science , metallurgy , composite material
The first asymmetric synthesis of the sesquiterpene quinones 3‐oxo‐ and 3β‐hydroxytauranin ( 1 , 2 ) was achieved and the originally proposed structure of 3α‐hydroxytauranin was revised. The protected benzyl chloride 5 was obtained in six steps starting from 4‐bromo‐3,5‐dihydroxybenzoic acid ( 8 ) via a highly scalable approach. The troublesome Negishi coupling of the benzyl chloride 5 with alkenyldimethylalane 6 was optimized to furnish all ‐ trans ‐farnesylarene 14 in very good yield. This prenylated arene was transformed in six additional steps to 3β‐hydroxytauranin ( 2 ). Finally, a new convenient access to propargylated terpenes without using dry cryogenic ammonia and gaseous allene or propyne is described.