GERANYL CHLORIDE

Submitted by Jose G. Calzada and John Hooz1 Checked by K.-K. Chan, A. Specian, and A. Brossi 

300-ml., three-necked flask is equipped with a magnetic stirring bar and reflux condenser (to which is attached a Drierite-filled drying tube) and charged with 90 ml. of carbon tetrachloride (Note 1) and 15.42 g. of geraniol (0.10 mole) (Note 2). To this solution is added 34.09 g. of triphenylphosphine (0.13 mole) (Note 3), and the reaction mixture is stirred and heated to reflux for 1 hour. This mixture is allowed to cool to room temperature dry pentane is added (100 ml.), and stirring is continued for an additional 5 minutes. 

The precipitate of triphenylphosphine oxide is filtered and washed with 50 ml. of pentane. The solvent is removed from the combined filtrate at the rotary evaporator under water aspirator pressure at room temperature. Distillation of the residue through a 2-cm. Vigreux column attached to a short-path distillation apparatus (Note 4) provides 13.0-14.0 g. (75-81%) of geranyl chloride, b.p. 47-49° (0.4 mm.), n23d = 1.4794 (Note 5). 

Carbon tetrachloride was dried over magnesium sulfate and distilled from phosphorus pentoxide through, a 25-cm. Vigreux column. Lower yields were obtained when either the glassware or reagents were not dried. 

The geraniol was purchased from Koch-Light Laboratories ( 98% pure), dried over potassium carbonate and distilled through 

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Geranyl chloride was prepared by treating geraniol, available from Aldrich Chemical Company, with carbon tetrachloride and triphenyl phosphine according to an Organic Syntheses procedure (Calzada, J. G. Hooz, J. Org. Si nth, 1974, 54, 63). 

Geraniol is converted into the isomeric alcohol, linalol, hy heat, and both alcohols yield the same chloride when treated wijth dry hydrochloric acid gas. Dupont and Labaune first prepared this chloride, which they considered was linalyl chloride, but Eorster and Cardwell have shown that it is geranyl chloride. 

By heating geranyl chloride with sodium alcoholate geranyl ethyl ethOr was obtained. This body, 10 17 - - CI2H5, is an oil with a faint rose odour, having the following characters —... 

Geranyl chloride can be prepared from geraniol by the careful use of triphenylphosphine in carbon tetrachloride. Tris(dimethylamino)phosphine reacts with carbon tetrachloride to form the complex (42) which can be used to form the enol esters (43) from acid anhydrides. Similarly, aldehydes form the alkenes (44), and esters or amides of trichloroacetic acid are converted to glycidic esters. ... 

Triphenylphosphine, m.p. 80-81°, was obtained from Eastman Organic Chemicals and was kept in a drying pistol held at approximately 65° (1 mm.) for approximately 18 hours prior to use. When only 10-20% excess triphenylphosphine was employed the yield of geranyl chloride was approximately 75%, but the small amount of unreacted geraniol which remained rendered product isolation more difficult. 

Geranyl chloride has been prepared by allylic rearrangement of lina-lool using hydrogen chloride in toluene solution at 100° or phosphorus... 

ALLYLIC CHLORIDES FROM ALLYLIC ALCOHOLS GERANYL CHLORIDE... 

Several comparative procedures are included. The formation of 1-BENZYLINDOLE and GERANYL CHLORIDE by two different procedures are representative. An interesting comparison of three of the recent adaptations of the Claisen rearrangement on the same substrate is presented in the preparations of N.N-DIMETHYL-5/ -CHOLEST-3-ENE-5-ACETAMIDE, ETHYL-5/S-CHOLEST-3-ENE-5-ACETATE, and 5/9-CHOLEST-3-ENE-5-ACETALDEHYDE. For the utility of the procedure itself as well as for comparison with previously presented syntheses, the preparation and use of triflates in the synthesis of CYCLOBUTANONE is included. 

Our sample of geranyl chloride was identical (i.r., n.m.r., and mass spectrum) with a sample prepared by an alternate route (Professor John Hooz, Department of Chemistry, University of Alberta). 

Treatment of allene (1,2-propadiene) with 2equiv. of butyllithium leads to an intermediate dilithio species which adds to ketones and aldehydes to afford homopropargylic alcohols in high yield (Table 9.3) [7]. This intermediate also reacts with geranyl chloride to afford the alkynyl coupling product uncontaminated by the allene regioisomer. 

The IR, NMR, and NMR spectra of this material are identical with those for distilled geranyl chloride (bp 49-51 C at 0.2 mm). Distillation on a small scale significantly reduces the yield, and there is no improvement in the yield of the phosphorylation reaction using distilled material. A synthesis of geranyl chloride was reported earlier in this series. We find, however, that the procedure of Corey, Kim, and Takeda is more convenient. 

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