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Catalytic Asymmetric Hydroboration/Amination and Alkylamination with Rhodium Complexes of 1,1′‐(2‐Diarylphosphino‐1‐naphthyl)isoquinoline
Author(s) -
Fernandez Elena,
Maeda Kenji,
Hooper Mark W.,
Brown John M.
Publication year - 2000
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/(sici)1521-3765(20000515)6:10<1840::aid-chem1840>3.0.co;2-6
Subject(s) - hydroboration , isoquinoline , rhodium , amination , chemistry , catalysis , organic chemistry
Catecholboronate esters formed by asymmetric hydroboration of arylalkenes are not directly converted to amines by reaction with hydroxylamine‐ O ‐sulfonic acid. Prior conversion to a trialkylborane by reaction with ZnEt 2 or MeMgCl permits a subsequent amination reaction to occur with essentially complete retention of configuration, leading to a range of primary α ‐arylalkylamines in up to 97 % enantiomeric excess ( ee ). Secondary, but not tertiary amines may be formed by a related pathway when in situ generated alkylchloramines are employed as the aminating agent. The catalytic asymmetric hydroboration, β ‐alkylation and amination steps may be combined in a single stage. Overall, this provides a practical procedure for the synthesis of enantiomerically enriched arylamines, exemplified inter alia by the synthesis of ( S )‐1,2,3,4‐tetrahydro‐1‐naphthylamine in 95–97 % ee and of ( R )‐ N ‐(cyclohexyl)‐1′‐(4‐methoxyphenyl)ethylamine in 93 % ee.