[7688-25-7]  · C28H28P2  · 1,4-Bis(diphenylphosphino)butane  · (MW 426.48)

(ligand for metal-catalyzed lactonization of unsaturated alcohols;1 allylic substitution;2 cyclization reactions;3 carbonylations;4 alkyne isomerization;5 alkyne-CO2 coupling6)

Alternate Name: dppb.

Physical Data: mp 135-137 °C.

Form Supplied in: white solid; widely available.

Handling, Storage, and Precautions: readily oxidized in solution to the phosphine oxide and should be handled under N2 or Ar. The compound is air-stable in the solid state.

Lactonization of Unsaturated Alcohols.

Allylic and propargylic alcohols can be converted to lactones by carbonylation using a catalyst prepared from Tris(dibenzylideneacetone)dipalladium and dppb (eq 1).1 Lactones are formed with secondary and tertiary alcohols. Primary allylic alcohols give a,b-unsaturated carboxylic acids (eq 2).

Allylic Substitution.

Alkylation of allyl acetates by dimethyl malonate derivatives is catalyzed by Palladium(II) Acetate-dppb (eq 3).2 Alkylation of the Pd(p-allyl) intermediate occurs exclusively at the terminal position. Regioselective addition to the internal position can be accomplished with (MeCN)3W(CO)3 in pyridine. Allylic azides can be prepared by reaction of Sodium Azide with allyl acetates using a catalyst prepared from Pd2(dba)3 and dppb (eq 4).7 Addition of dimethyl sodiomalonate to 1-chloro-1-vinylcyclopropanes results in methylenecyclopropanes (eq 5).8

Cyclization Reactions.

Synthesis of pyrrolidines and furans by intramolecular allylation of alkenes is catalyzed by Bis(1,5-cyclooctadiene)nickel(0)-dppb (eq 6).3 Macrocyclization to give the 21-membered ring was catalyzed by Tetrakis(triphenylphosphine)palladium(0)-dppb (eq 7).9

Hydroacylation Reactions.

Carbonylation of vinylarenes with formate esters is catalyzed by Pd(PPh3)4-dppb under CO. A mixture of linear and branched esters is formed from the reaction of p-methylstyrene and n-butyl formate (eq 8).4 Hydroformylation of unsaturated amides is catalyzed by Rh(PPh3)3(CO)H and dppb to give nitrogen heterocycles (eq 9).10

Alkyne Isomerizations.

Isomerization of alkynones to dienones was catalyzed by Pd(OAc)2-dppb (eq 10).5 The (E,E)-diene was stereoselectively formed.

Alkyne-CO2 Coupling.

Nickel(0) complexes of dppb catalyze the coupling of alkynes with carbon dioxide to give pyrones (eq 11).6 Bicyclic products can be formed by coupling of CO2 with diynes.11

1. El Ali, B.; Alper, H. JOC 1991, 56, 5357.
2. Trost, B. M.; Lautens, M.; Hung, M. H.; Carmichael, C. S. JACS 1984, 106, 7641.
3. (a) Oppolozer, W.; Bedoya-Zurita, M.; Switzer, C. Y. TL 1988, 29, 6433. (b) Oppolozer, W.; Keller, T. H.; Kuo, D. L.; Pachinger, W. TL 1990, 31, 1265.
4. Lin, I. J. B.; Alper, H. CC 1989, 248.
5. Trost, B. M.; Schmidt, T. JACS 1988, 110, 2301.
6. Inoue, Y.; Itoh, Y.; Hashimoto, H. CL 1978, 633.
7. Murahashi, S.-I.; Taniguchi, Y.; Imada, Y.; Tanigawa, Y. JOC 1989, 54, 3292.
8. McGaffin, G.; Michalski, S.; Stolle, A.; Braese, S.; Salauen, J.; De Meijere, A. SL 1992, 7, 558.
9. Trost, B. M.; Cossy, J. JACS 1982, 104, 6881.
10. Ojima, I.; Korda, A.; Shay, W. R. JOC 1991, 56, 2024.
11. Tsuda, T.; Suniya, R.; Saegusa, T. SC 1987, 17, 147.

Gregory T. Whiteker

Union Carbide Corporation, South Charleston, WV, USA

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