0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login to access the full content or check if you have access via Variation 1: Using Triphenylphosphine and Tetrachloromethane

DOI: 10.1055/sos-SD-035-00055

Margaretha, P.Science of Synthesis, (20073579.

This variation is now generally used for converting alcohols into chlorides, the reactions taking place under mild, essentially neutral conditions. Because it proceeds with inversion of configuration, it is a simple device for converting optically active alcohols into chiral chlorides in high optical purity. Tetrachloromethane generally serves both as solvent and halogen source, but in some instances the tetrachloride has been replaced by hexachloroethane or by trichloroacetic acid derivatives (when ester or nitrile groups are present).[‌65‌,‌66‌] The byproduct, triphenylphosphine oxide, usually precipitates completely and is easily removed by filtration. On occasion, a difficulty may be encountered in separating the alkyl halide from the accompanying phosphine oxide, but this is usually resolved by adding an inert solvent such as pentane to ensure precipitation of the phosphine oxide. Because triphenylphosphine reacts with tetrachloromethane in the absence of alcohols, the success of this variation depends critically on the initial presence of an alcohol to avoid the formation of triphenylphosphine dichloromethylene ylide. In a representative example, 1-chloro-3,7-dimethylocta-2,6-diene (geranyl chloride, 30) is obtained by heating geraniol (29) in tetrachloromethane at reflux with triphenylphosphine (Scheme 25).[‌67‌] After distillation, the chloro compound is obtained in 7581% yield. This same variation can be used for the (stereoselective) preparation of enantiomerically pure pheromone precursors. Thus, all four enantiomers of 1-chloro-2,4-dimethyloctane and of 1-chloro-2,6-dimethyloctane can be obtained in very good yields from the corresponding (C2 inverted) alcohol precursors.[‌68‌,‌69‌] Similarly, racemic 1-chloro-2-methylheptane is obtained in >90% yield,[‌70‌] whereas 1-chloro-4-methyldodecane (31) is obtained from 4-methyldodecan-1-ol in 85% yield (Scheme 25).[‌71‌]

Meeeee 88 Meeeeeeee ee Meeeeee Meeeeeee ee 8-Meeeee-8-eeeeeeeeeeeeee eeee eee Meeeeeeeeee Meeeeeee[‌88‌,‌88‌]

Meeeeee eeeeeeeeeeee eeeeeeeeeeee ee M8 ee 8,8-eeeeeeeeeeeeeee eeeeeeee eeeeeeee eeee eeeeeeeeeee eeeeeeeee ee e (eeeeeeeeeeeee) eeeeeee eeeee ee M8, eee eeeeee ee eeeeeeeeeeeeeeeeee eee eeeeeeeeeeeeeeeeee eeeeeeee eeeeeee eee eeee eeeeeeeee. Meee, eee eeeeeee 88 eeeeee eeee eeee eeeeeeeeeee ee eeeeeeee ee eeeeee ee eeee 8-eeeeee-8,8-eeeeeeeeeeeeeeeeee (88) ee 88% eeeee (Meeeee 88).[‌88‌] Meeee eeeeeeeee eeeeeeee eeeee eeeeeeeee, eee ee eeeeeeee eeee eee eeeeeeee eeeeeeee eeeeeeeee, e eeeeeeee ee eeeeeeeeeeeeeeeeee/eeeeeeeeeeeeeeeeee eeee eee eeeeeeee eeeeeee 88 eeeee eee eeeeeeee eeeeeeee 88 (Meeeee 88).[‌88‌]

Meeeee 88 Meeeeeeeeeee Meeeeeeeeeeee ee Meeeeeeee Meeeeeee eeee Meeeeeeeeeeeeeeeee/Meeeeeeeeeeeeeeeee[‌88‌,‌88‌]

Mee ee eee eeee eeee eeee-eeeeeeeee eeeeeeeeee eeeeee eee eee eeeeeeee, eeee eeeeeeeee eee eeee eeeee eeee eee eee eeeeeeeee ee eeeeeeeee eeeeee eeeeeeeee 8,8:8,8-ee-M-eeeeeeeeeeeeee-8-eeeeee-8-eeeee-α-M-eeeeeeeee,[‌88‌] 8,8:8,8-ee-M-eeeeeeeeeeeeee α-M-eeeeeeeeeeeeee eeeeeeee,[‌88‌] eeeeee 8-eeeeee-8-eeeee α-M-eeeeeeeeeeeeeee (88%), 8-eeeeee-8-eeeee α-M-eeeeeee (88%), eee 8,8-eeeeeeee-8,8-eeeeeeeeeeeeee (88%).[‌88‌] M-Meeeeeeee 8-eeeee-8-eeeeeeeeeeeeeeeeeee eee eeee eeeeeeeee eeee eee eeeeeeeeeeeee eeeeeeeee ee eeeeeeeeee (ee. 8888%) eeeeee.[‌88‌] Me eeeeeeee, eee eeeeeee eeeeeee eeeee ee eee eeeeeeeeee 88 eee ee eeeeeeeeeee eeeeeeee ee eeeeeeee (Meeeee 88).[‌88‌]

Meeeee 88 Meeeeeeee ee 8-Meeeee-8-eeeeeeeeeeee[‌88‌]

Meeeeeeeeeee Meeeeeeee

8-Meeeee-8-eeeeeeeeeeeeee (88):[‌88‌]

8-Meeeeeeeeeeee-8-ee (88.8e, 8.888eee), Me8M (88.8e, 8.888eee), eee MMe8 (88.8e, 8.888eee) (MMMMMMM: eeeee) eeee eeeeee ee 888°M eeee eeeeeeee, ee eeeee eeeeeeeeeee e eeeeee eeeeeeeeee eeeeeeee eeeeee (MMMMMMM). Meeee 8e, MeMM (8.8eM, 8.88eee) eee MMe8 (8.8e, 8.888eee) eeee eeeee ee eee eeeeeee ee 888°M, eee eeeeeeee eee eeeeeeeee eee ee eeeeeeeeee 88eee, eeeee eee eeeeeee eee eeee ee eee eeee eeeeeeeeeee. Mee eeeeeeeeee eee eeee eeeeee eee eeeeeee (888eM) eee eeeee, eeeeee ee eee eeeeeeee, eee eee eeeee eee eeeeeeeee eee eeeeee eeee eeeeeee. Meeeeee ee eee eeeeeee eeee eee eeeeeeee eeeeeeee eee eeeeeeee eeee ee eee, eeeee eee eeeeeeee ee eeeeeeeeeeeeee eee eeeeeeeeeeee (8888°M/8.8Meee); eeeee: 88.8e (88%).