References
<A NAME="RG24502ST-1">1</A>
Camps P.
Muñoz-Torrero D.
Muñoz-Torrero V.
Tetrahedron Lett.
1995,
36:
1917
<A NAME="RG24502ST-2A">2a</A>
Burton RD.
Bartberger MD.
Zhang Y.
Eyler JR.
Schanze KS.
J.
Am. Chem. Soc.
1996,
118:
5655
<A NAME="RG24502ST-2B">2b</A>
Chen LH.
Farahat MS.
Gaillard ER.
Farid S.
Whitten DG.
J. Photochem. Photobiol. A: Chem.
1996,
95:
21
<A NAME="RG24502ST-2C">2c</A>
Kellett MA.
Whitten DG.
Res.
Chem. Intermed.
1995,
21:
587
<A NAME="RG24502ST-2D">2d</A>
Gan H.
Kellett MA.
Leon JW.
Kloeppner L.
Leinhos U.
Gould IR.
Farid S.
Whitten DG.
J.
Photochem. Photobiol. A: Chem.
1994,
82:
211
<A NAME="RG24502ST-3">3</A>
Yuste F.
Origel AE.
Breña LJ.
Synthesis
1983,
109
<A NAME="RG24502ST-4A">4a</A>
Benhaliliba H.
Derdour A.
Bazureau J.-P.
Texier-Boullet F.
Hamelin J.
Tetrahedron Lett.
1998,
39:
541
<A NAME="RG24502ST-4B">4b</A>
Harris CE.
Lee LY.
Dorr H.
Singaram B.
Tetrahedron
Lett.
1995,
36:
2921 ;
and references therein
<A NAME="RG24502ST-5">5</A>
Lopez L.
Troisi L.
Tetrahedron Lett.
1992,
48:
7321
<A NAME="RG24502ST-6">6</A>
García-Valverde M.
Pedrosa R.
Vicente M.
García-Granda S.
Gutiérrez-Rodríguez A.
Tetrahedron
1996,
52:
10761
<A NAME="RG24502ST-7">7</A>
García-Valverde M.
Nieto J.
Pedrosa R.
Vicente M.
Tetrahedron
1999,
55:
2755
For oxidations under air in strongly
basic solutions, see:
<A NAME="RG24502ST-8A">8a</A>
Elkik E.
Bull.
Soc. Chim. Fr.
1959,
933
<A NAME="RG24502ST-8B">8b</A>
Russell GA.
Bemis AG.
J.
Am. Chem. Soc.
1966,
88:
5491
<A NAME="RG24502ST-8C">8c</A>
Gersmann HR.
Bickel AF.
J.
Chem. Soc. B
1971,
2230
<A NAME="RG24502ST-8D">8d</A>
Neumann R.
Sasson Y.
J. Org. Chem.
1984,
49:
1282
<A NAME="RG24502ST-9">9</A>
Typical experimental procedure: The
amino alcohol (1a-k) (0.1 g) was
added to a stirred suspension of KOH (1.0 g) in diethyl ether (20
mL). The stirring was continued for the proper time (Table
[1]
) at room temperature.
The solid was filtered off and washed with ether. The solvent was
removed to yield the amide. The solid was dissolved in water and
the solution acidified with HCl and extracted with ether. The organic
layer was dried and the solvent was removed to yield the corresponding
carboxylic acid.
The starting amino alcohols were
purchased from the usual suppliers (1e: 1-dimethylamino-2-propanol, 1f: N-methylephedrine, 1j: 2-dimethylamino-2-methyl-1-propanol, 1k: 1-methyl-2-piperidinemethanol) or synthesized
by literature procedures:
<A NAME="RG24502ST-10A">10a</A>
1a (2-dimethylamino-1-propanol):
Rosnati V.
Gazz. Chim. Ital.
1950,
80:
663
<A NAME="RG24502ST-10B">10b</A>
1b (2-Dibenzylamino-1-propanol)
and 1i (2-Dibenzylamino-2-methyl-1-propanol):
Kerwin JF.
Ullyot GE.
Fuson RC.
Zirkle CL.
J. Am. Chem. Soc.
1947,
69:
2961
<A NAME="RG24502ST-10C">10c</A>
1c (2-Dimethylamino-1-butanol):
Halverstadt IF.
Hardie WR.
Willians AR.
J.
Am. Chem. Soc.
1959,
81:
3618
<A NAME="RG24502ST-10D">10d</A>
1d (2-Dimethylamino-2-phenylethanol):
Miyano S.
Lu LD.-L.
Viti SM.
Sharpless KB.
J. Org. Chem.
1985,
50:
4350
<A NAME="RG24502ST-10E">10e</A>
1g (2-Dibenzylamino-1-phenyl-1-propanol):
Schwan TJ.
Lougheed GS.
Burrous SE.
J.
Heterocyclic Chem.
1974,
11:
807
<A NAME="RG24502ST-10F">10f</A>
1h (2-Butylamino-1-phenyl-1-propanol):
Soai K.
Yokoyama S.
Hayasaka T.
J. Org. Chem.
1991,
56:
4264
<A NAME="RG24502ST-11">11</A> The resulting amides 2a,
2f (dimethylacetamide); 2b, 2g (dibenzylacetamide); 2h (dibutylacetamide); 2c (dimethyl-propanamide); 2d (dimethylbenzamide); 2e (dimethyl-formamide); 2k (1-methyl-2-piperidone) are commercial products
or described in literature; 2l (1-acetylpyrrol-idine):
Al-Sehemi AG.
Atkinson RS.
Fawcett J.
J. Chem.
Soc., Perkin Trans 1
2002,
257
<A NAME="RG24502ST-12A">12a</A>
Huber JE.
Tetrahedron Lett.
1968,
3271
<A NAME="RG24502ST-12B">12b</A>
Foote CS.
Dzakpasu AA.
Lin JW.-P.
Tetrahedron Lett.
1975,
1247
<A NAME="RG24502ST-12C">12c</A>
Wasserman HH.
Terao S.
Tetrahedron
Lett.
1975,
1735
<A NAME="RG24502ST-13A">13a</A> The
starting amino ketones were purchased from the usual suppliers (4e: 1-dimethylamino-2-propanone); synthesized
by literature procedures. 4f (2-dimethylamino-1-phenyl-1-propanone):
Welle F.
Verevkin SP.
Keller M.
Beckhaus H.-D.
Ruechardt C.
Chem. Ber.
1994,
127:
697
<A NAME="RG24502ST-13B">13b</A>
4l (α-Phenyl-α-pyrrolidinoacetophenone):
Heinzelman RV.
Aspergren BD.
J. Am. Chem. Soc.
1953,
75:
3409 ; or synthesized by known methods
<A NAME="RG24502ST-13C">13c</A>
4h: (2-Dibutylamino-1-phenyl-1-propanone):
Pyridinium chlorochromate (1.29 g, 6 mmol) was added in small portions
to a stirred solution of amino alcohol 1h (0.39
g, 1.5 mmol) in CH2Cl2 (30 mL) over 4 Å sieves.
The resulting mixture was stirred at r.t. for 6 h and filtered.
The solvent was evaporated under reduced pressure. The residue was dissolved
in an aqueous solution of NaOH (15% w/v, 10 mL) and
extracted with ether. The organic layer was separated, washed with
brine and dried (Na2SO4). Removal of the solvent
left a residue, which was purified by column chromatography (hexane/EtOAc,
6:1) to yield amino ketone 4h (67%).
Colorless liquid. bp 82-84 (0.2 mmHg). IR (neat, cm-1):
1685. 1H NMR (CDCl3, 200 MHz): 0.79
(t, 6 H, J = 12 Hz); 1.04-1.21
(m, 7 H), 1.22-1.38 (m, 4 H); 2.40 (t, 4 H, J = 12 Hz); 4.31 (q, 1 H, J = 9.0 Hz); 7.22-7.50
(m, 3 H); 7.94-8.00 (m, 2 H). 13C
NMR (CDCl3, 50 MHz): 9.2 (CH3); 14.0 (CH3);
20.4 (CH2); 30.7 (CH2); 50.7 (CH2);
60.4 (CH); 128.1 (CHAr);128.9 (CHAr); 132.4
(CHAr); 137.0 (CAr); 201.8 (CO). MS (m/z, %):
260 (M+ - 1, 1), 156(100). Anal. Calcd for
C17H27NO: C, 78.11; H, 10.41; N, 5.36. Found:
C, 78.22; H, 10.63; N, 5.27.
<A NAME="RG24502ST-14A">14a</A>
Turaeva DA.
Kurbatov YV.
Russ. J. Org. Chem.
1999,
1092
<A NAME="RG24502ST-14B">14b</A>
Turaeva DA.
Kurbatov YV.
Kurbatova AS.
Russ. J. Org. Chem.
1995,
739
<A NAME="RG24502ST-15">15</A>
The EPR studies were made on the reaction
mixtures without filtration. Moreover, the evolution of the EPR
spectra taken at different reaction times showed the presence of
mixtures of radicals as intermediates in these reactions.
<A NAME="RG24502ST-16A">16a</A>
Neelakantan L.
J. Org. Chem.
1971,
36:
2256
<A NAME="RG24502ST-16B">16b</A>
Alcaide B.
López-Mardomingo C.
Pérez-Ossorio R.
Plumet J.
J. Heterocyclic
Chem.
1982,
19:
45
<A NAME="RG24502ST-16C">16c</A>
Wu MJ.
Pridgen LN.
Synlett
1990,
636
<A NAME="RG24502ST-16D">16d</A>
Aylward JB.
Quart. Rev.
1971,
25:
407
<A NAME="RG24502ST-16E">16e</A>
Royer J.
Hüsson HP.
J. Org. Chem.
1985,
50:
636
<A NAME="RG24502ST-17">17</A>
NOESY experiments showed that the
angular oxazolidine proton at C-7a was trans to
the proton at C-6, indicating an S configuration
at this carbon. (2S,3R,6S,7aR)-6-Benzyl-2-phenyl-3-methyl-5-oxo-2,3,5,6,7,7a-hexahydro-pyrrolo-[2,1-b]-oxazole (5).
White solid, mp 101-103 ºC. [α]23
D +34.6
(c 1.6, CHCl3). IR (neat, cm-1)
1700. 1H NMR (CDCl3, 300 MHz): 1.00
(d, J = 6.8 Hz, 3 H), 2.19-2.23
(m, 2 H), 2.88 (dd, J = 13.2
Hz, 8.2 Hz, 1 H), 3.06-3.18 (m, 2 H), 3.95 (qd, J = 6.9 Hz, 6.8 Hz, 1 H), 4.95
(t, J = 5.4 Hz, 1 H), 5.19 (d, J = 7.1 Hz, 1 H), 7.20-7.37
(m, 5 H, HAr). 13C NMR (CDCl3,
75 MHz): 13.4 (CH3), 30.7 (CH2), 37.6 (CH2),
48.6 (CH), 54.7 (CH), 85.3(CH), 91.2 (CH), 126.6 (CHAr),
128.0 (CHAr), 128.3 (CHAr), 128.5 (CHAr),
129.1 (CHAr), 136.3 (CAr), 138.5 (CAr),
175.5 (CO). Anal.calcd for C20H21NO2:
C, 78.15; H, 6.89; N, 4.56. Found: C, 77.77; H, 7.08; N, 4.35.
<A NAME="RG24502ST-18">18</A>
Two isomers were observed at room
temperature. (R)-1-Acetyl-2-benzyl pyrrolidine
(2m). Colorless oil. [α]D
23 +25.54
(c 1.1, CHCl3), IR (neat,
cm-1) 1650. MS (m/z, %): 203
(M+, 32), 91(28), 43(100). 1H
NMR (CDCl3, 300 MHz): 1.53-1.75 (m, 2 H), 1.95-2.05
(m, 8 H), 2.41-2.52 (m, 2 H), 2.62-2.69 (m, 4
H), 3.03-3.12 (m, 2 H), 3.33-3.58 (m, 4 H), 3.61-3.68
(m, 2 H), 7.14-7.33 (m, 5 H, HAr). 13C
NMR (CDCl3, 75 Mz): 22.2 (CH3), 22.4 (CH3),
30.4 (CH2), 31.7 (CH2), 39.0 (CH2),
39.6 (CH), 41.1 (CH), 45.1 (CH2), 46.9 (CH2),
50.7 (CH2), 52.5 (CH2), 126.2 (CHAr),
126.3 (CHAr), 128.4 (CHAr), 128.5 (CHAr),
128.6 (CHAr), 139.9 (CAr), 169.2 (CO). Anal.
Calcd for C13H17NO: C, 76.81; H, 8.43; N, 6.89.
Found: C, 76.70; H, 8.62; N, 6.76.
