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DOI: 10.1055/s-2002-32962
A New Convenient Method for the Preparation of Enamides from N-Allylamides
Publication History
Publication Date:
25 July 2002 (online)
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Abstract
Isomerization of various N-allylamides in the presence of Fe(CO)5 smoothly afforded the corresponding enamides in yields up to 95%. The reported procedure is compatible with various functional groups including protected amino and hydroxy groups. The possible mechanism of transformation is discussed.
Key words
enamides - N-allylamides - double bond shift - iron pentacarbonyl
- 1
Wenkert E.Hudlicky T.Showalter HD. J. Am. Chem. Soc. 1978, 100: 4893 - 2
Tsuda Y.Isobe K.Ukai A. J. Chem. Soc., Chem. Commun. 1971, 1554 - 3
Becker Y.Eisenstadt A.Stille JK. J. Org. Chem. 1980, 45: 2145 - 4
Bach T. Angew. Chem., Int. Ed. Engl. 1996, 35: 884 - 5
Kinderman SS.van Maarseveen JH.Schoemaker HE.Hiemstra H.Rutjes FP. Org. Lett. 2001, 3: 2045 -
6a
Breederveld H. Recl. Trav. Chim. Pays-Bas 1960, 79: 401 -
6b
Breederveld H. Recl. Trav. Chim. Pays-Bas 1960, 79: 1197 -
7a
Lenz GR. Synthesis 1978, 489 -
7b
Campbell AL.Lenz GR. Synthesis 1987, 421 - 8
Meth-Cohn O.Westwood KT. J. Chem. Soc., Perkin Trans. 1 1984, 1173 -
9a
Suen YH.Horeau A.Kagan HB. Bull. Soc. Chim. Fr. 1965, 1454 -
9b
Kagan HB.Horeau A.Suen YH. Bull. Soc. Chim. Fr. 1965, 1457 -
10a
Eiden F.Nagar BS. Arch. Pharm. (Weinheim, Ger.) 1964, 297: 367 -
10b
Eiden F.Nagar BS. Arch. Pharm. (Weinheim, Ger.) 1963, 296: 458 -
10c
Eiden F.Nagar BS. Arch. Pharm. (Weinheim, Ger.) 1963, 296: 445 - 11
Ben-Ishai D.Giger R. Tetrahedron. Lett. 1965, 4523 -
12a
Kurtz P.Disselnkötter H. Liebigs Ann. Chem. 1972, 764: 69 -
12b
Brettle R.Shibib SM.Wheeler KJ. J. Chem. Soc., Perkin Trans. 1 1985, 831 -
13a
Fürstner A.Dierkes T.Thiel OR.Blanda G. Chem.-Eur. J. 2001, 7: 5286 -
13b
Stefanuti I.Smith SA.Taylor RJK. Tetrahedron Lett. 2000, 41: 3735 -
13c
Shen R.Porco JA. Org. Lett. 2000, 2: 1333 - 14
Larock RC. Comprehensive Organic Transformations Wiley; New York: 1999. - 15
Stille JK.Becker Y. J. Org. Chem. 1980, 45: 2139 - 17
Hubert J.Moniotte P.Goebbels G.Warin R.Teyssié P. J. Chem. Soc., Perkin Trans. 2 1973, 1954 - Boc2NH represents an exellent alternative to the classical Gabriel method for preparation of amines from halides:
-
18a
Grehn L.Ragnarson U. Synthesis 1987, 285 -
18b
Grehn L.Ragnarson U. Acc. Chem. Res. 1991, 24: 285 ; and references cited therein - 25
N-Allylphthalimide
afforded N-(prop-1-enyl)-phthalimide (E/Z 10:
1) in 99% yield after 15 h at 100 °C.
Interestingly, our results were in disagreement with those of Rossi
and Barola, reporting only partial conversion of some N-allylimides with Fe(CO)5:
Rossi P.Barola PF. Ann. Chim. 1969, 59: 762
References
This work is a part of the Ph.D. Thesis of S. Sergeyev, University of Zürich, 2002.
19We have shown that the use of Cs2CO3 as the phase-transfer catalyst allows to avoid the preparation of Na or K salt of Boc2NH, see ref. [18a]
20
Preparation of N
-(2-Methylprop-2-enyl)-3-phenylpropanamide
9a (Typical Procedure for the Preparation of Substituted N
-Allylamides
9a-d). A mixture of 6a (4.0
mL, 40 mmol), Boc2NH (4.34 g, 20 mmol), Cs2CO3 (6.52
g, 20 mmol), and DMF (20 mL) was stirred for 12 h at r.t., then
the volatile materials were removed in vacuo. The residue was partitioned
between CH2Cl2 (75 mL) and H2O
(50 mL), the organic phase was separated and washed with H2O
(2 × 50 mL), dried (MgSO4), and concentrated
to afford crude 7a. It was dissolved in CH2Cl2 (20
mL) and treated with TFA (6.1 mL, 80 mmol) in one portion. After
4 h stirring at r.t. the mixture was concentrated and the residue
was dried in vacuo to give crude 8a as
TFA salt. It was dissolved in the mixture of CH2Cl2 (75
mL) and Et3N (8.3 mL, 60 mmol) and treated dropwise at
0 °C with 3-phenylpropanoyl chloride (2.83 mL, 19
mmol). The mixture was stirred for 1 h at 0 °C,
then allowed to reach r.t., washed with H2O (25 mL),
10% aq citric acid (25 mL), again H2O (2 × 25
mL), and dried (MgSO4). Evaporation of the solvent in
vacuo and crystallization of the residue from hexane/EtOAc
afforded 9a (3.82 g, 94% total
yield after 3 steps). Slightly yellow solid, mp 51-52 °C.
1H
NMR (CDCl3): δ = 1.65 (s, 3 H, Me),
2.51 (t, 2 H, J = 7.7 Hz,
CH2CO), 2.96 (t, 2 H, J = 7.7
Hz, CH
2Ph), 3.75 (d, 2 H, J = 6.0 Hz,
CH2N), 4.68, 4.76 (2 s-like m, 2 H, CH2=C),
5.80 (br s, NH), 7.15-7.28 (m, 5 H, Ph). 13C
NMR (CDCl3): δ = 20.1 (Me), 31.6 (CH2Ph), 38.3 (CH2CO), 44.9 (CH2N), 110.7
(CH2=C), 126.1 (arom.
CH), 128.2 (2 arom. CH), 128.4 (2 arom. CH), 140.7 (C), 141.8 (C),
172.0 (C=O). CI-MS (NH3): m/z (%) = 407(29) [2
M + 1]+, 221(25) [M + NH4]+,
204(100) [2 M + 1]+.
Preparation of
2a/2a′ (Typical Procedure for the Isomerization
of N
-Allylamides
to N
-Prop-1-enylamides). A
mixture of 1a (945 mg, 5 mmol) and Fe(CO)5 (0.2
mL, 1 mmol) was stirred under Ar for 16 h at 100 °C.
The mixture was allowed to reach r.t., then the catalyst was removed
in vacuo and collected in a trap, cooled by liquid N2.
Content of the trap was treated with 5% alcoholic FeCl3 solution
to destroy toxic Fe(CO)5. The residue in the reaction
flask was dissolved in CHCl3 and filtered through Celite.
Evaporation of the solvent in vacuo and column chromatography of
the residue on silica gel (CH2Cl2/EtOAc
10:1) afforded 2a (548 mg, 58%)
and 2a′ (350 mg, 37%),
total yield of 2a/2a′ 95%.
(
E
)-3-Phenyl-
N
-prop-1-enyl-propanamide(2a). Colorless solid,
mp 113-114.5 °C.
1H
NMR (CDCl3): δ = 1.62 (dd, 3 H, J = 1.7, 6.7
Hz, Me), 2.49 (t, 2 H, J = 7.8
Hz, CH2CO), 2.95 (t, 2 H, J = 7.8
Hz, CH
2Ph), 5.09 (qd, 1 H, J = 6.7, 14.2
Hz, CH=CHN), 6.71-6.78
(m, 1 H, CH=CHN), 7.15-7.28
(m, 5 H, Ph), 7.40 (br d, NH). 13C
NMR (CDCl3): δ = 14.7 (Me), 31.4 (CH2Ph), 38.1 (CH2CO), 107.8 (CH=CHN), 123.1 (CH=CHN), 126.2 (arom. CH), 128.2 (2 arom.
CH), 128.4 (2 arom. CH), 140.6 (arom. C), 169.2 (C=O).
CI-MS (NH3): m/z (%) = 207(37)[M + NH4]+),
190(100) [M + 1]+).
(
Z
)-3-Phenyl-
N
-prop-1-enyl-propanamide (2a′). Colorless
solid, mp 53.5-55 °C.
1H
NMR (CDCl3): δ = 1.49 (dd, 3 H, J = 1.5, 7.0
Hz, Me), 2.57 (t, 2 H, J = 7.7
Hz, CH2CO), 2.96 (t, 2 H, J = 7.7
Hz, CH
2Ph), 4.73 (qd, 1 H, J = 7.0, 8.9
Hz, CH=CHN), 6.64-6.71
(m, 1 H, CH=CHN), 7.16-7.28
(m, 6 H, Ph, NH). 13C NMR (CDCl3): δ = 10.7
(Me), 31.4 (CH2Ph), 38.0 (CH2CO), 105.3 (CH=CHN), 121.8 (CH=CHN), 126.2 (arom. CH), 128.2 (2 arom.
CH), 128.5 (2 arom. CH), 140.5 (arom. C), 169.5 (C=O).
CI-MS (NH3): m/z (%) = 207(48) [M + NH4]+, 190(100) [M + 1]+).
E/Z ratio was determined from the integral intensities of the signals of CH=CHN, (E)- or (Z)-configuration of double bond was assigned based on the value of coupling constants (typically 13.5-14.2 Hz for (E)- and 8.5-9.0 Hz for (Z)-enamides).
23It should be noted, that our findings are in contrast with those of Stille and Becker, reported decomposition of N-(3,3-dimethylallyl)acetamide upon the action of Fe(CO)5, see ref. [15]
24Prepared by alkylation of 1a with MeI in DMF in the presence of NaH.
26N-Tosylallylamine remained unchanged upon the action of Fe(CO)5.