Abstract
The first example of an intramolecular enantioselective Michael
addition of nitronates onto conjugated systems utilizing a chiral
phase-transfer catalyst is described. A range of five-membered γ-nitro
esters with up to three stereocentres have been prepared and the
relative and absolute configurations proven by chemical and crystallographic
methods. The products are rapidly obtained and are precursors to
five-membered cyclic γ-amino acids.
Key words
organocatalysis - phase transfer - intramolecular - nitronate - Michael addition
References and Notes
1a Gellman SH.
Acc. Chem. Res.
1998,
31:
173
1b Guo L.
Almeida AM.
Zhang W.
Reidenbach AG.
Choi
SH.
Guzei IA.
Gellman SH.
J. Am. Chem. Soc.
2010,
132:
7868
1c Guo L.
Chi YG.
Almeida AM.
Guzei IA.
Parker BK.
Gellman SH.
J.
Am. Chem. Soc.
2009,
131:
16018
2a Cheng RP.
Gellman SH.
DeGrado WF.
Chem. Rev.
2001,
101:
3219
2b Hill DJ.
Mio MJ.
Prince RB.
Hughes TS.
Moore JS.
Chem. Rev.
2001,
101:
3893
2c Seebach D.
Beck AK.
Bierbaum DJ.
Chemistry & Biodiversity
2004,
1:
1111
2d Seebach D.
Gardiner J.
Acc. Chem. Res.
2008,
41:
1366
2e Ghosh AK.
Bilcer G.
Schiltz G.
Synthesis
2001,
2203
2f List B.
Castello C.
Synlett
2001,
1687
3a Bautista AD.
Appelbaum JS.
Craig CJ.
Michel J.
Schepartz A.
J. Am. Chem. Soc.
2010,
132:
2904
3b Horne WS.
Boersma MD.
Windsor MA.
Gellman SH.
Angew.
Chem. Int. Ed.
2008,
47:
2853
3c Murray JK.
Gellman SH.
Biopolymers
2007,
88:
657
3d Sadowsky JD.
Fairlie WD.
Hadley EB.
Lee HS.
Umezawa N.
Nikolovska-Coleska Z.
Wang SM.
Huang DCS.
Tomita Y.
Gellman SH.
J. Am. Chem. Soc.
2007,
129:
139
4 Nodes WJ.
Nutt DR.
Chippindale AM.
Cobb AJA.
J.
Am. Chem. Soc.
2009,
131:
16016 ;
for an excellent alternative method, see ref. 1c
5 Hashimoto T.
Maruoka K.
Chem. Rev.
2007,
107:
5656
6 Zhang F.-Y.
Corey EJ.
Org. Lett.
2000,
2:
1097
7 Lygo B.
Allbutt B.
Kirton EHM.
Tetrahedron
Lett.
2005,
46:
4461
8a Shibuguchi T.
Fukuta Y.
Akachi Y.
Sekine A.
Ohshima T.
Shibasaki M.
Tetrahedron
Lett.
2002,
43:
9539
8b Ohshima T.
Shibuguchi T.
Fukuta Y.
Shibasaki M.
Tetrahedron
2004,
60:
7743
9a Ooi T.
Fujioka S.
Maruoka K.
J. Am. Chem. Soc.
2004,
126:
11790
9b Ooi T.
Takada S.
Fujioka S.
Maruoka K.
Org. Lett.
2005,
7:
5143
10a Marsh GP.
Parsons PJ.
McCarthy C.
Cornique
XG.
Org. Lett.
2007,
9:
2613
10b Yasuhara T.
Nishimura K.
Osafune E.
Muraoka O.
Kiyoshi T.
Chem. Pharm.
Bull.
2004,
52:
1109
11 Assigned both by comparison to the ¹ H
NMR of a related compound (see ref. 10a) and by analogous assignment
of trans crystals of compound 22 (as shown by X-ray crystallography).
12 Kerr MS.
Read de Alaniz J.
Rovis T.
J. Am. Chem.
Soc.
2002,
124:
10298
13
Typical Procedure
for Organocatalytic Cyclization
Ethyl
2-[(1
S
,2
R
)-2-nitrocyclopentyl]acetate (2)
E )-ethyl-7-nitrohept-2-enoate (1 , 50.3 mg, 0.25 mmol) in toluene (3 mL)
was added phase-transfer catalyst 11 (10
mol%) and K2 CO3 (7 mg, 0.05 mmol).
The resulting solution was stirred for 18 h at 23 ˚C. After
this time, the solvent was removed under reduced pressure to give
a pale yellow oil that was subjected to flash column chromatography
(SiO2 ; Et2 O-hexane, 1:4). The resulting colourless
oil (50.3 mg, 0.25 mmol, quant.) was analyzed by chiral HPLC analysis [Chiralcel
OD; 0.46 cm ø × 25 cm; hexane-propan-2-ol
(96:4); 1 mL min-¹ ; t
R (major
diastereo-mer) = 7.06 min, 7.63 min; t
R (minor diastereomer) = 8.03 min,
8.69 min]. [α]D -3.1
(c 1, CHCl3 ). ¹ H
NMR (400 MHz, CDCl3 ): 1.24-1.28 (3 H, J = 7.2 Hz, CH
3 ),
1.35-2.37 (6 H, cyclopent-H ),
2.42 (2 H, m, CH
2 CO2 Et),
2.91 (1 H, hex, J = 8.8 Hz,
CH CH2 CO2 Et), 4.14
(2 H, q, J = 7.2 Hz, CH2 CH3 ), 4.81
(1 H, m, CHNO2 ) [NB: the 1S ,2S signal appears as a multiplet at δ = 5.01].
IR: 2979, 1732, 1547, 1373, 1269, 1187, 1028, 913, 734, 648 cm-¹ .
HRMS: m/z calcd for C9 H15 NO4 Na+ :
224.0893; found: 224.0894.
14 X-ray crystal structural information
(CCDC 789178) available from the Cambridge Crystallographic Data
Centre (CCDC) at http://www.ccdc.cam.ac.uk.
