In:
Chemistry – A European Journal, Wiley, Vol. 11, No. 1 ( 2005-01), p. 361-368
Abstract:
A synthetic route to enantiomerically pure (1 R ,2 S )‐1‐phenylphospholane‐2‐carboxylic acid ( 1 ), which is a phosphorus analogue of proline, has been established. A key step is the deprotonation–carboxylation of the 1‐phenylphospholane borane complex 3 by using s BuLi/1,2‐dipiperidinoethane (DPE). Configurational stability of the key intermediate, the amine‐coordinated α‐phosphinoalkyllithium borane complex 4 , was investigated by employing lithiodestannylation–carboxylation of both diastereomers of the 1‐phenyl‐2‐trimethylstannylphospholane borane complex 7 in the presence of several kinds of amines, and as a result, 4 was found to be configurationally labile even at −100 °C. The key intermediate, the DPE‐coordinated trans ‐1‐phenyl‐2‐phospholanyllithium borane complex 9 , was isolated, and the structure was identified by X‐ray crystal structure analysis. This is the first X‐ray crystal structure determined for an α‐monophosphinoalkyllithium borane complex. Remarkably, the alkyllithium complex is monomeric and tricoordinate at the lithium center with a slightly pyramidalized environment, and the existence of a LiC bond (2.170 Å) has been confirmed. Moreover, 1 H– 7 Li HOESY and 6 Li NMR analyses suggested the structure of 9 in solution as well as the existence of an equilibrium between 9 , its cis isomer, and the ion pair 8 at room temperature, which was extremely biased towards 9 at −100 °C. Finally, 1 was used as a chiral ligand in a palladium‐catalyzed allylic substitution, and the desired product was obtained in high yield with good enantioselectivity.
Type of Medium:
Online Resource
ISSN:
0947-6539
,
1521-3765
DOI:
10.1002/chem.200400631
Language:
English
Publisher:
Wiley
Publication Date:
2005
detail.hit.zdb_id:
1478547-X
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