A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1985, 63, 203
DOI: 10.15227/orgsyn.063.0203
Submitted by Pierre Crabbé, Bahman Nassim, and Maria-Teresa Robert-Lopes1.
Checked by Jeffrey S. Stults and Edwin Vedejs.
1. Procedure
In a 500-mL, three-necked flask, equipped with a thermometer, stirrer, and a reflux condenser with drying tube, are placed 12.6 g (0.1 mol) of 1-octyn-3-ol, 154 mL of dioxane, 7.24 g (0.0504 mol) of cuprous bromide, 7.4 g of paraformaldehyde, and 18.54 g (0.183 mol) of diisopropylamine (Note 1). The resulting mixture is gently refluxed and stirred for 2 hr and then cooled to room temperature and filtered through a Celite plug. The dark-brown filtrate is concentrated under vacuum (Rotavapor) to a gummy residue and then diluted with 50 mL of water followed by 100 mL of ether and acidified with 6 N hydrochloric acid to pH 2. The ether–water layers are decanted from any residue, the ether layer is separated, and the aqueous solution is extracted with ether (5 × 50 mL). The ether extracts are combined and washed with small portions of water until pH 6.5 is reached. The organic layer is then washed with saturated sodium chloride solution and dried over anhydrous MgSO4. After removal of ether by distillation through a 20-cm Vigreux column (water aspirator vacuum) while heating on a water bath, ≤40°C, the residual liquid is fractionated under reduced pressure through a 10-cm Vigreux column. The main fraction is collected at 41–42.5°C(0.15 mm) to give 8.65 g of pure allene (Note 2), with additional fractions of a less pure material.
2. Notes
1. Cuprous bromide and 1-octyn-3-ol were used as supplied by the Aldrich Chemical Company, Inc. Dioxane was dried over sodiumbenzophenone and distilled, and diisopropylamine was distilled from barium oxide.
2. The spectral properties of 4-hydroxynona-1,2-diene are as follows: IR (neat) cm−1: 3500 (OH), 1960 (C=C=C), 850 (=CH), 2900–2850 (CH). 1H NMR (CDCl3) δ: 0.65–1.7 (m); 4.15 (1 H, m); 4.8 (2 H, d of d, J = 2.6 Hz); 5.22, (1 H, q, J = 6 Hz).
3. Discussion
Although allenes were characterized long ago as a distinct class of organic substances, they have only recently received proper attention from chemists, in particular for their potential in organic synthesis.2 3 4 A number of methods are known for the transformation of acetylenes into allenes,5 but few are known to allow the homologation of an acetylenic group into a propadiene functionality.
A general procedure for the homologation of acetylenic compounds into allenes is described. The reaction conditions are mild and appear to be general, so that they can be applied to plain acetylenic substances as well as to acetylenic alcohols, ethers, and esters. This procedure is essentially a one-step reaction. As such, it is simpler and faster than the previously reported technique that involves the conversion of an acetylenic compound into the Mannich base, the formation of its quaternary ammonium salt and the reduction of this salt with lithium aluminum hydride.6 Of great advantage over previously available methodology are the mild conditions, as well as the clean and fast procedure, which make this a method of choice for an efficient conversion of acetylenes to allenes.7 8 9

References and Notes
  1. Department of Chemistry, University of Missouri, Columbia, MO 65211.
  2. Taylor, D. R. Chem. Rev. 1967, 67, 317 and references cited therein.
  3. Griesbaum, K. Angew. Chem. Int. Ed. Engl. 1966, 5, 933;
  4. Mavrov, M. V.; Kucherov, V. F. Russ. Chem. Rev. 1967, 36, 233.
  5. Fischer, H. In "The Chemistry of Alkenes," Patai, S., Ed.; Wiley-Interscience: New York, 1964; Chapter 13, p. 1025.
  6. Galantay, E.; Basco, I.; Coombs, R. V. Synthesis 1974, 344.
  7. Crabbé, P.; André, D.; Fillion, H. Tetrahedron Lett. 1979, 893;
  8. Crabbé, P.; Fillion, H.; André, D.; Luche, J. L. J. Chem. Soc., Chem. Commun. 1979, 859;
  9. Searles, S.; Li, Y.; Nassim, B.; Lopes, M. T.; Tran, P. T.; Crabbé, P. J. Chem. Soc., Perkin Trans. 1 1984, 747.

Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

hydrochloric acid (7647-01-0)

ether (60-29-7)

sodium chloride (7647-14-5)

barium oxide

Benzophenone (119-61-9)

sodium (13966-32-0)

cuprous bromide (7787-70-4)

MgSO4 (7487-88-9)

dioxane (123-91-1)

propadiene (463-49-0)

lithium aluminum hydride (16853-85-3)

diisopropylamine (108-18-9)

1,2-Nonadien-4-ol (73229-28-4)

1-octyn-3-ol (818-72-4)

paraformaldehyde (30525-89-4)