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Carboboration Reactions of 1,2‐Bis[(diarylphosphino)ethynyl]benzenes with Tris(pentafluorophenyl)borane
Author(s) -
Liedtke René,
Kehr Gerald,
Fröhlich Roland,
Daniliuc Constantin G.,
Wibbeling Birgit,
Petersen Jeffrey L.,
Erker Gerhard
Publication year - 2012
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.201200495
Subject(s) - chemistry , borane , carbocation , benzene , medicinal chemistry , acetylene , derivative (finance) , lewis acids and bases , crystal structure , tris , boranes , stereochemistry , catalysis , crystallography , organic chemistry , boron , biochemistry , financial economics , economics
The 1,2‐bis[(diarylphosphino)ethynyl]benzene derivatives 1a (R=Ph) and 1b (R= o ‐tolyl) undergo 1,1‐carboboration at one of their acetylene units upon treatment with (C 6 F 5 ) 3 B at elevated temperature to give the products 5a and 5b , respectively. At room temperature, we observed the formation of the corresponding phosphireniumborate zwitterions, 7a and 7b , respectively, which may be intermediates of the 1,1‐carboboration reactions. The reaction of the more bulky 1,2‐bis[(dimesitylphosphino)ethynyl]benzene 1c with (C 6 F 5 ) 3 B takes a different course. At 110°, we observed the complete conversion to the benzopentafulvene derivative 8 which is probably formed in a typical carbocation rearrangement sequence after the initial (C 6 F 5 ) 3 B Lewis acid‐addition step. The compounds 5a, 5b, 7b , and 8 were characterized by X‐ray crystal‐structure analyses.