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Preparation of THP‐Ester‐Derived Pyridinium‐Type Salts and their Reactions with Various Nucleophiles
Author(s) -
Fujioka Hiromichi,
Minamitsuji Yutaka,
Moriya Takahiro,
Okamoto Kazuhisa,
Kubo Ozora,
Matsushita Tomoyo,
Murai Kenichi
Publication year - 2012
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201200234
Subject(s) - pyridinium , chemistry , nucleophile , anomer , reagent , stereoselectivity , salt (chemistry) , nucleophilic substitution , organic chemistry , substitution reaction , medicinal chemistry , catalysis
Nucleophilic substitution at the anomeric positions of tetrahydropyranyl (THP) and related carbohydrate‐derived esters that proceeded through pyridinium‐type salt intermediates have been developed. Treatment of the 6‐substituted α‐acetoxy‐tetrahydropyrans with TMSOTf (TMS=trimethylsilyl) and 2‐substitutited pyridines, such as 2‐ p ‐tolylpyridine and 2‐methoxypyridine, led to the efficient generation of cis ‐pyridinium‐type salts. These salts reacted with various nucleophiles, such as alcohols, azides, and organozinc reagents, to form nucleophilic‐substitution products. A characteristic feature of these processes was that they took place under mild conditions, which did not affect acid‐labile protecting groups. Furthermore, the reactions that employed azides and C‐nucleophiles generated 2,6‐ trans products with high degrees of stereoselectivity.