Bis(triphenylphosphine)copper(I) Cyanoborohydride


[51321-47-2]  · C37H33BCuNP2  · Bis(triphenylphosphine)copper(I) Cyanoborohydride  · (MW 627.98)

(selective, mild reducing reagent for the conversion of acid chlorides to aldehydes under neutral conditions, and reduction of aldehydes and ketones to alcohols in acidic media)

Alternate Name: m-bis(cyanotrihydroborato)tetrakis(triphenylphosphine)dicopper(I).

Physical Data: white, nonhydroscopic solid, mp 176-177 °C; exists as a dimer.1

Solubility: sol acetone, CHCl3, and THF; insol water, ethanol, and ether.

Preparative Method: from treating Copper(II) Sulfate or Copper(I) Chloride sequentially with excess Triphenylphosphine and Sodium Cyanoborohydride in ethanol.2 The reagent is synthesized in an analogous manner to those described for the preparation of the corresponding BH4 derivative, Bis(triphenylphosphine)copper(I) Borohydride, substituting NaBH3CN for NaBH4.3

Functional Group Reductions.

Under neutral conditions this reagent selectively reduces alkyl and aryl acid chlorides to aldehydes without further conversion to alcohols (Table 1).2

In acidic (pH 3) media, aldehydes and ketones (except diaryl) are reduced to alcohols (Table 2). Reduction of 4-t-butylcyclohexanone under these conditions provides the trans isomer with 94:6 selectivity (eq 1).2 The stereoselectivity of this reduction is among the highest observed for hydride reagents.4

The ease and convenience of conducting reactions coupled with the excellent chemoselectivity possible under neutral conditions recommend this reagent for conversion of acid chlorides to aldehydes. No other functional groups are known to be reduced at ambient temperature.

Related Reagents.

Bis(triphenylphosphine)copper(I) Borohydride.

1. Melmed, K. N.; Li, T.; Mayerle, J. J.; Lippard, S. J. JACS 1974, 96, 69.
2. Hutchins, R. O.; Markowitz, M. TL 1980, 21, 813.
3. (a) Fleet, G. W. J.; Fuller, C. J.; Harding, P. J. C. TL 1978, 1437. (b) Fleet, G. W. J.; Harding, P. J. C. TL 1979, 975. (c) Sorrell, T. N.; Pearlman, P. S. JOC 1980, 45, 3449. (d) Lippard, S. J.; Welcker, P. S. IC 1972, 11, 6.
4. (a) Review of stereochemistry of hydride reductions of ketones: Boone, J. R.; Ashby, E. C. Top. Stereochem. 1979, 11, 53. (b) The same high selectivity for the trans isomer (trans/cis 94/6) is observed with (Ph3P)2CuBH4 in acidic media: Fleet, G. W. J.; Harding, P. J. C. TL 1981, 22, 675.

Robert O. Hutchins

Drexel University, Philadelphia, PA, USA

MaryGail K. Hutchins

LNP Engineering Plastics, Exton, PA, USA

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