2,2,2-Trichloroethyl trans-1,3-Butadiene-1-carbamate1

[77627-82-8]  · C7H8Cl3NO2  · 2,2,2-Trichloroethyl trans-1,3-Butadiene-1-carbamate  · (MW 244.51)

(a diene which provides regio- and stereoselective control in Diels-Alder reactions1)

Physical Data: mp 70-71 °C; IR (KBr): cm-1 3350, 1710, 1660, 1540, 710; 1H NMR (CDCl3): d 7.0-5.3 (m), 5.2-4.8 (m), 4.68 (s); 13C NMR: d 150.7, 132.8, 124.9, 113.3, 112.7, 93.8, 73.5.2

Preparative Method: the synthesis of trans-1,3-butadienecarbamates utilizes a modified Curtius rearragement.3,4 In the synthesis of 2,2,2-trichloroethyl trans-1,3-butadiene-1-carbamate, Malonic Acid and Acrolein were condensed in pyridine to obtain trans-2,4-pentadienoic acid in 44-51% yield (eq 1).5 This compound, which may be stored in a freezer for several months,4 was treated with Ethyl Chloroformate and the resulting mixed anhydride transformed into the azide derivative. Due to the explosive nature, the azide was not isolated but immediately added to a refluxing solution of 2,2,2-Trichloroethanol in toluene. Purification by silica gel column chromatography (hexane-ethyl acetate = 9:1) then afforded the title compound.4

Diels-Alder Reactions.

2,2,2-Trichloroethyl trans-1,3-butadiene-1-carbamate, like the related N,N-dialkyl- and N-acyl-N-alkyl-1,3-dienes,6-11 are masked dienamines for Diels-Alder reactions. The advantage of this reagent, however, is that it is thermally more stable than the N,N-dialkyl-1,3-dienes and, hence, capable of giving higher yields even with poor dienophiles.1a,12 In addition, the carbamate protecting group is removed under relatively mild conditions (activated Zinc-Acetic Acid, rt, 24 h), providing higher yields of the amine product (eq 2).2 Like other 1,3-diene-1-carbamates,13-15 the title compound also gives excellent regio- (ortho) and stereo- (endo) selectivity in Diels-Alder reactions.2,12,16 Its reaction with ethyl atropate, which gives exclusively a product possessing the acylamino and aryl groups in a cis orientation,12 has been exploited in an elegant, stereospecific synthesis of (±)-tilidine (eq 2).2 Noteworthy is the stereochemical outcome of this Diels-Alder reaction, which was opposite to that provided by the related N,N-dialkyl-1-amino-1,3-dienes.1b,17

Related Reagents.

Benzyl 1,3-Butadiene-1-carbamate.

1. (a) Oppolzer, W. COS 1991, 5, 315. (b) Hickmott, P. T 1984, 40, 2989. (c) Overman, L. E. ACR 1980, 13, 218.
2. Overman, L. E. Petty, C. B. Doedens, R. J. JOC 1979, 44, 4183.
3. Overman, L. E.; Clizbe, L. A. JACS 1976, 98, 2352.
4. Oppolzer, W.; Frostl, W. HCA 1975, 58, 587.
5. Overman, L. E.; Taylor, G. F.; Jessup, P. J. TL 1976, 3089.
6. Oppolzer, W.; Frostl, W. HCA 1975, 58, 587.
7. Oppolzer, W.; Bieber, L.; Francotte, E. TL 1979, 981.
8. Oppolzer, W.; Bieber, L.; Francotte, E. TL 1979, 4537.
9. Kiefer, H. S 1972, 39.
10. Snowden, R. L. TL 1984, 3835.
11. Mezzetti, A.; Nitti, P.; Pitacco, G.; Valentin, E. T 1985, 41, 1415.
12. Overman, L. E.; Freerks, R. L.; Petty, C. B.; Clizbe, L. A.; Ono, R. K.; Taylor, G. F.; Jessup, P. J. JACS 1981, 103, 2816.
13. Overman, L. E.; Jessup, P. J. JACS 1978, 100, 5179.
14. Overman, L. E.; Jessup, P. J. TL 1977, 1253.
15. Overman, L. E.; Fukaya, C. JACS 1980, 102, 1454.
16. Overman, L. E.; Taylor, G. F.; Houk, K. N.; Domelsmith, L. N. JACS 1978, 100, 3182.
17. Satzinger, G. LA 1969, 728, 64.

Theresa A. Devlin & David J. Jebaratnam

Northeastern University, Boston, MA, USA

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