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Reaction of Frustrated Lewis Pairs with Ketones and Esters
Author(s) -
Xu BaoHua,
Yanez Raul Alfonso Adler,
Nakatsuka Hiroshi,
Kitamura Masato,
Fröhlich Roland,
Kehr Gerald,
Erker Gerhard
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.201100960
Subject(s) - chemistry , nucleophile , borane , frustrated lewis pair , alkyl , stereochemistry , triple bond , medicinal chemistry , aryl , intermolecular force , tautomer , bond cleavage , conjugated system , double bond , lewis acids and bases , molecule , organic chemistry , catalysis , polymer
The frustrated Lewis pair (FLP) Mes 2 PCH 2 CH 2 B(C 6 F 5 ) 2 ( 1 ) reacts with an enolizable conjugated ynone by 1,4‐addition involving enolate tautomerization to give an eight‐membered zwitterionic heterocycle. The conjugated endione PhCO‐CHCH‐COPh reacts with the intermolecular FLP t Bu 3 P/B(C 6 F 5 ) 3 by a simple 1,4‐addition to an enone subunit. The same substrate undergoes a more complex reaction with the FLP 1 that involves internal acetal formation to give a heterobicyclic zwitterionic product. FLP 1 reacts with dimethyl maleate by selective overall addition to the CC double bond to give a six‐membered heterocycle. It adds analogously to the triple bond of an acetylenic ester to give a similarly structured six‐membered heterocycle. The intermolecular FLP P( o ‐tolyl) 3 /B(C 6 F 5 ) 3 reacts analogously with acetylenic ester by trans ‐addition to the carbon–carbon triple bond. An excess of the intermolecular FLP t Bu 3 P/B(C 6 F 5 ) 3 , which contains a more nucleophilic phosphane, reacts differently with acetylenic ester examples, namely by OC(alkyl) bond cleavage to give the {R‐CO 2 [B(C 6 F 5 ) 3 ] 2 − }[alkyl‐P t Bu 3 + ] salts. Simple aryl or alkyl esters react analogously by using the borane‐stabilized carboxylates as good leaving groups. All essential products were characterized by X‐ray diffraction.

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