Synthesis of optically active cyclopalladated complexes of primary benzylamine derivatives, (R)-(-)-2-phenylglycine methyl ester and (±)-1-phenylethylamine
Abstract
Cyclopalladation of optically active α-monosubstituted primary
benzylamines such as 2-phenylglycine methyl ester and 1-phenylethylamine
has been studied. Palladium(II) acetate reacted with
(R)-2-phenylglycine methyl ester hydrochloride to give the
chloro-bridged dinuclear cyclopalladated complex
(R,R)-[{Pd(µ-Cl)(C
6
H
4
CHCO
2
MeNH
2
)}
2
] 1, whereas
with (R)- or (S)-1-phenylethylamine
palladium(II) acetate afforded the acetato-bridged dinuclear
cyclopalladated complex (R,R)- or
(S,S)-[{Pd(µ-O
2
CMe)(C
6
H
4
CHMeNH
2
)}
2
] from which
the chloro-bridged dinuclear complex (R,R)- or
(S,S)-[{Pd(µ-Cl)(C
6
H
4
CHMeNH
2
)}
2
] was obtained by
metathetical reaction with sodium chloride. Complexes 1 and
[{Pd(µ-Cl)(C
6
H
4
CHMeNH
2
)}
2
] were converted into mononucler cyclopalladated
complexes
(R)-[PdCl(C
6
H
4
CHCO
2
MeNH
2
)(dmpy)],
(R)-[PdCl(C
6
H
4
CHCO
2
MeNH
2
)(PPh
3
)] and (R)- or
(S)-[PdCl(C
6
H
4
CHMeNH
2
)(dmpy)],
by the bridge-splitting reactions with 3,5-dimethylpyridine (dmpy) and
triphenylphosphine. The crystal structure of
(R)-[PdCl(C
6
H
4
CHCO
2
MeNH
2
)(PPh
3
)] has been determined. A short contact between
the amino group and carbonyl group probably represents a hydrogen
bond.
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