Propargyl Aldehyde

[624-67-9]  · C3H2O  · Propargyl Aldehyde  · (MW 54.05)

(conjugate acceptor; dienophile)

Alternate Names: 2-propynal; propiolaldehyde.

Physical Data: bp 59-61 °C.

Solubility: sol H2O, alcohol, ether, benzene, toluene, acetone.

Form Supplied in: not commercially available.

Preparative Method: most simply prepared by oxidation of Propargyl Alcohol.1,2

Handling, Storage, and Precautions: great care should be taken in handling the neat liquid as an explosion has been reported.3 The explosion was attributed to rapid polymerization, probably catalyzed by base or a radical initiator. It is recommended that handling of 2-propynal should include the use of a nonglass container and dilution with a sufficient volume of an inert solvent to absorb the heat of polymerization without boiling, e.g. <=10% in toluene. Use in a fume hood.

Addition to the Carbonyl Group.

Grignard reagents add well to 2-propynal, as in the preparation of 1-hexyn-5-en-3-ol (eq 1).4 Aryl Grignard reagents also add successfully.5 Although most heteronucleophiles add in a conjugate fashion (see next section), aniline has been reported to form the corresponding imine.6 A pyrrole synthesis has been developed which relies on an aldol reaction of 2-propynal with a 3-silyl-2-azetidinone (eq 2).7

Addition to the Triple Bond.

Conjugate additions of nucleophiles based on oxygen (eq 3),8,9 nitrogen (eq 4),10 and sulfur (eq 5)11 leading to 3-substituted acroleins have been reported.


2-Propynal reacts as a typical dienophile in Diels-Alder reactions with a variety of dienes. Nucleophilic dienes add without catalysis (eqs 6 and 7).12,13 Some dienes require Lewis-acid catalysis to react, as in the preparation of ansa-secosteroids (eq 8).14

Lanthanide salts catalyze the 1,2-cycloaddition of 2-propynal to ketene imines (eq 9).15 Sodium Azide cycloadds to 2-propynal across the triple bond, yielding a 1,2,3-triazole.16


Heating 2-propynal with 3-amino-2-cyclohexenones provides a simple route to tetrahydroquinoline derivatives as in eq 10.17,18 Tetraazaannulenes may be prepared simply by heating o-phenylenediamines with 2-propynal (eq 11).19

Related Reagents.

3-Butyn-2-one; 3,3-Diethoxy-1-propyne; Ethyl Lithiopropiolate; Methyl Propiolate; Propargyl Alcohol.

1. Sauer, J. C. OSC 1962, 4, 813.
2. See also: Ghelfi, F.; Grandi, R.; Pagnoni, U. M. SC 1992, 22, 1845.
3. Makula, D.; Lamy, P. Actual. Chim. 1983, 31 (CA 1984, 100, 197 104z).
4. Newman-Evans, R. H.; Simon, R. J.; Carpenter, B. K. JOC 1990, 55, 695.
5. Wulff, W. D.; Tang, P. C.; Chan, K. S.; McCallum, J. S.; Yang, D. C.; Gilbertson, S. R. T 1985, 41, 5813.
6. Shubina, U. V.; Tikhomirov, D. A.; Eremeev, A. V. KGS 1984, 2, 184.
7. Thielman, M.; Winterfeldt, E. H 1984, 22, 1161.
8. Gunatilaka, A. A. L.; Hirai, N.; Kingston, D. G. I. TL 1983, 24, 5457.
9. See also: Hodgson, S. T.; Hollinshead, D. M.; Ley, S. V. T 1985, 41, 5871.
10. Johnson, F.; Pillai, K. M. R.; Grollman, A. P.; Tseng, L.; Takeshita, M. JMC 1984, 27, 954.
11. Hanko, R.; Hammond, M. D.; Fruchtmann, R.; Pfitzner, J.; Place, G. A. JMC 1990, 33, 1163.
12. Gorgues, A.; Simon, A.; Le Cog, A.; Hercouet, A.; Corre, F. T 1986, 42, 351.
13. Thiemann, T.; Kohlstruk, S.; Schwär, G.; De Meijere, A. TL 1991, 32, 3483.
14. Prelle, A.; Winterfeldt, E. H 1989, 28, 333.
15. Barbaro, G.; Battaglia, A.; Giorgianni, P. JOC 1988, 53, 5501.
16. Fan, R. Huadong Huagong Xueyuan Xuebao 1984, 121 (CA 1984, 101, 151 802t).
17. Caprathe, B. W.; Jaen, J. C.; Wise, L. D.; Heffner, T. G.; Pugsley, T. A.; Meltzer, L. T.; Parvez, M. JMC 1991, 34, 2736.
18. See also: LeBel, N. A.; Caprathe, B. W. JOC 1985, 50, 3938.
19. Sakata, K.; Nakamura, H.; Hashimoto, M. ICA 1984, 83, L67.

Patrick Perlmutter

Monash University, Clayton, Victoria, Australia

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