Abstract
Unprotected samarium acetamide and chloroacetamide enolates were
prepared by treatment of iodoacetamide and dichloroacetamide with
SmI2 . The addition of these samarium-based enolates to
aldimines was efficiently performed affording 3-aminoamides and
3-amino-2-chloroamides in high yields. A mechanism is proposed to
explain the synthesis and reactivity of samarium enolates of primary
amides.
Key words
amides - enolates - samarium
References and Notes
1a </A>
Petragnani N.
Yonashiro M.
Synthesis
1982,
521
1b </A>
Thompson CM.
Green DLC.
Tetrahedron
1991,
47:
4223
<A NAME="RG13810ST-2">2 </A>
Concellón JM.
Concellón C.
J.
Org. Chem.
2006,
71:
4428
<A NAME="RG13810ST-3">3 </A>
Concellón JM.
Concellón C.
J.
Org. Chem.
2006,
71:
1728
2 :
4a </A>
Soderquist JA.
Aldrichimica Acta
1991,
24:
15
4b </A>
Molander GA.
Chem. Rev.
1992,
92:
29
4c </A>
Molander GA. In
Comprehensive Organic
Synthesis
Vol. 1:
Trost BM.
Fleming I.
Pergamon;
Oxford:
1991.
p.251-282
4d </A>
Molander GA. In
Organic Reactions
Paquette LA.
John
Wiley;
New York:
1994.
p.211-367
4e </A>
Molander GA.
Harris CR.
Chem.
Rev.
1996,
96:
307
4f </A>
Molander GA.
Harris CR.
Tetrahedron
1998,
54:
3321
4g </A>
Krief A.
Laval AM.
Chem. Rev.
1999,
99:
745
4h </A>
Steel PG.
J. Chem. Soc., Perkin Trans. 1
2001,
2727
4i </A>
Kagan HB.
Tetrahedron
2003,
59:
10351
4j </A>
Concellón JM.
Rodríguez-Solla H.
Chem.
Soc. Rev.
2004,
33:
599
4k </A>
Concellón JM.
Rodríguez-Solla H.
Eur.
J. Org. Chem.
2006,
1613
4l </A>
Rudkin IM.
Miller
LC.
Procter DJ.
Organomet. Chem.
2008,
34:
19
4m </A>
Nicolau KC.
Ellery SP.
Chen JS.
Angew. Chem. Int. Ed.
2009,
48:
7140
<A NAME="RG13810ST-5">5 </A>
Concellón JM.
Rodríguez-Solla H.
Concellón C.
Simal C.
Alvaredo N.
J. Org. Chem.
2010,
75:
3451
6a </A>
Concellón JM.
Rodríguez-Solla H.
Simal C.
Adv. Synth.
Catal.
2009,
351:
1238
6b </A>
Concellón JM.
Rodríguez-Solla H.
Simal C.
del Amo V.
García-Granda S.
Díaz MR.
Adv. Synth. Catal.
2009,
351:
2991
7 </A>
For a recent review on samarium enolates,
see ref. 4l.
<A NAME="RG13810ST-8">8 </A> For the synthesis of N -tosylimines, see:
Wang Y.
Song J.
Hong R.
Li H.
Deng L.
J. Am. Chem.
Soc.
2006,
128:
8156
<A NAME="RG13810ST-9">9 </A> The 0.1 M solution of samarium diiodide
in THF was rapidly and readily prepared according to our reported
method:
Concellón JM.
Rodríguez-Solla H.
Bardales E.
Huerta M.
Eur. J. Org.
Chem.
2003,
1775
<A NAME="RG13810ST-10">10 </A>
General Procedure
for the Synthesis of 3-Aminoamides 1
A solution of
iodoacetamide 3 (0.4 mmol) and the corresponding N -tosylaldimine 2 (0.4
mmol) in THF (2 mL) was treated with a 0.1 M solution of SmI2 in
THF (10 mL, 1 mmol). After 3.5 h at r.t. the reaction mixture was
quenched with HCl (1.0 M, 20 mL). Usual workup and purification
by flash column chromatography (hexane-EtOAc, 3:1) afforded
pure compounds 1 .
<A NAME="RG13810ST-11">11 </A>
Enholm EJ.
Forbes DC.
Holub DP.
Synth. Commun.
1990,
20:
981
2 , see:
12a </A>
Concellón JM.
Rodríguez-Solla H.
Huerta M.
Pérez-Andrés JA.
Eur. J. Org. Chem.
2002,
1839
12b </A>
Concellón JM.
Huerta M.
Tetrahedron
Lett.
2002,
43:
4943
<A NAME="RG13810ST-13">13 </A>
General Procedure
for the Synthesis of 3-Amino-2-chloroamides 4
Diiodomethane
(2.4 equiv) was added dropwise to a suspension of the corresponding
imine 2 (1.0 equiv), dichloroacetamide
(1.0 equiv), and samarium powder (2.4 equiv) in THF (25 mL) at r.t.
After stirring for 3.5 h at the same temperature, the corresponding
3-amino-2-choro-amides 4 were obtained
after usual workup and purification by flash column chromatography
(hexane-EtOAc = 3:1).
<A NAME="RG13810ST-14">14 </A>
Molander GA. In
Comprehensi ve Organic
Synthesis
Vol. 1:
Trost BM.
Fleming I.
Schreiber SL.
Pergamon;
Cambridge:
1991.
p.252
<A NAME="RG13810ST-15">15 </A>
Concellón JM.
Pérez-Andrés JA.
Rodríguez-Solla H.
Angew.
Chem. Int. Ed.
2000,
39:
2773
<A NAME="RG13810ST-16">16 </A>
Concellón JM.
Pérez-Andrés JA.
Rodríguez-Solla H.
Chem.
Eur. J.
2001,
7:
3062
