References and Notes
For pioneering works, see:
1a
Oppolzer W.
Keller K.
Tetrahedron Lett.
1970,
1117
1b
Wildman WC.
Slabaugh MR.
J. Org. Chem.
1971,
36:
3202
For recent examples, see:
2a
Abiko A.
Liu J.-F.
Wang G.
Masamune S.
Tetrahedron Lett.
1997,
38:
3261
2b
Baskaran S.
Aurich HG.
Synlett
1998,
277
2c
Sharma GVM.
Srinivas RI.
Goverdhan RV.
Rama RAV.
Tetrahedron: Asymmetry
1999,
10:
229
2d
Falb E.
Bechor Y.
Nudelman A.
Hassner A.
Albeck A.
Gottlieb HE.
J. Org. Chem.
1999,
64:
498
2e
Dransfield PJ.
Moutel S.
Shipman M.
Sik V.
J. Chem. Soc., Perkin Trans. 1
1999,
3349
2f
Noguchi M.
Okada H.
Tanaka M.
Matsumoto S.
Kakehi A.
Yamamoto H.
Bull. Chem. Soc. Jpn.
2001,
74:
917
2g
Cheng Q.
Zhang W.
Tagami Y.
Oritani T.
J. Chem. Soc., Perkin Trans. 1
2001,
452
2h
Singh S.
Ishar MPS.
Singh G.
Singh R.
Can. J. Chem.
2005,
83:
260
3 For a theoretical study on oximenitrone isomerization, see: Long JA.
Harris NJ.
Lammertsma K.
J. Org. Chem.
2001,
66:
6762
4a
Grigg R.
Thianpantagul S.
J. Chem. Soc., Perkin Trans. 1
1984,
653
4b
Shirai M.
Kuwabara H.
Matsumoto S.
Yamamoto H.
Kakehi A.
Noguchi M.
Tetrahedron
2003,
59:
4113
5 For related palladium-catalyzed cycloaddition of oximes, see: Frederickson M.
Grigg R.
Thornton-Pett M.
Redpath J.
Tetrahedron Lett.
1997,
38:
7777
6a
Tamura O.
Mitsuya T.
Ishibashi H.
Chem. Commun.
2002,
1128
6b
Tamura O.
Mitsuya T.
Huang X.
Tsutsumi Y.
Hattori S.
Ishibashi H.
J. Org. Chem.
2005,
70:
10720
7 For a review on related N -metalloazomethine ylides, see: Husineca S.
Savic V.
Tetrahedron: Asymmetry
2005,
16:
2047
For related cycloaddition of acylhydrazones, see:
8a
Wilson RM.
Rekers JW.
J. Am. Chem. Soc.
1979,
101:
4005
8b
Kobayashi S.
Shimizu H.
Yamashita Y.
Ishitani H.
Kobayashi J.
J. Am. Chem. Soc.
2002,
124:
13678
8c
Kobayashi S.
Hirabayashi R.
Shimizu H.
Ishitani H.
Yamashita Y.
Tetrahedron Lett.
2003,
44:
3351
8d
Yamashita Y.
Kobayashi S.
J. Am. Chem. Soc.
2004,
126:
11279
8e
Shirakawa S.
Lombardi PJ.
Leighton JL.
J. Am. Chem. Soc.
2005,
127:
9974
9 For completion of the cycloaddition, 2 equiv of BF3 ·OEt2 are essential. See ref. 6.
10 During study on the intramolecular cycloaddition of N -boranonitrone, we observed the tendency that electron-rich carbon atom in the olefin attacks the nitrone-carbon. For example, reaction of oxime 15a with BF3 ·OEt2 afforded cycloadduct 16 bearing a bicyclo[3.3.0] system, whereas a similar reaction of oxime 15b afforded cycloadduct 17 having a bicyclo[3.2.1] system (Scheme
[7 ]
). See ref 6b.
Scheme 7
11 Adachi I, Yamamori T, and Hiramatsu Y. inventors; Jpn. Patent, 50939.
12
Preparation of Ethyl 2-[
tert
-Butyldimethylsilyl-oxyimino]acetate (12) : The mixture of ethyl 2-hydroxy-iminoacetate (11 ;11 0.91 g, 7.8 mmol), tert -butylchloro-dimethylsilane (1.77 g, 11.8 mmol), and imidazole (1.60 g, 23.5 mmol) in DMF (12 mL) was stirred at r.t. for 46 h. The reaction mixture was poured into H2 O and extracted with Et2 O. The combined organic phases were washed with brine and dried with MgSO4 . The solvent was removed by rotary evaporation and the crude product was purified by column chromatography on silica gel with hexane-Et2 O (20:1) to afford 12 (1.77 g, 98%) as a colorless oil. IR: 2934, 1749, 1728 cm-1 . 1 H NMR (300 MHz, CDCl3 ): δ = 7.62 (s, 1 H), 4.30 (q, J = 7.1 Hz, 2 H), 1.33 (t, J = 7.1 Hz, 3 H), 0.95 (s, 9 H), 0.23 (s, 6 H). 13 C NMR (75 MHz, CDCl3 ): δ = 162.3, 146.1, 61.3, 25.7, 18.0, 14.0, -5.4. LRMS: m /z = 231.14. HRMS (EI): m /z calcd for C10 H21 NO3 Si: 231.1291; found: 231.1270.
13
Typical Procedure for the Cycloaddition : To a solution of 12 (300 mg, 1.3 mmol) in DCE (10 mL) were added 7e (1.1 mL, 13 mmol) and BF3 ·OEt2 (310 µL, 2.9 mmol) at r.t., and then the mixture was heated at 60 °C for 2 h. The reaction was monitored by TLC. After cooling, the reaction mixture was poured into sat. NaHCO3 solution and was extracted with CHCl3 . The combined organic layers were washed with brine and dried with MgSO4 . The residue was concentrated under reduced pressure. The crude product was purified by chromatography on silica gel with hexane-EtOAc (3:2) to give two diastereomers, 14e (160 mg, 61%) and 14e′ (47 mg, 18%) as light brown oils. 14e : IR (neat): 1733 cm-1 . 1 H NMR (300 MHz, CDCl3 ): δ = 5.90 (br s, 1 H), 4.23 (q, J = 7.1 Hz, 2 H), 4.12 (d, J = 7.5 Hz, 1 H), 2.73 (dd, J = 7.0, 14.5 Hz, 1 H), 1.82-1.72 (m, 4 H), 1.59-1.45 (m, 2 H), 1.40 (s, 3 H), 1.29 (t, J = 7.1 Hz, 3 H). 13 C NMR (75 MHz, CDCl3 ): δ = 164.4, 95.5, 66.0, 61.1, 55.7, 39.5, 28.2, 26.4, 24.8, 14.2. LRMS: m /z = 199. HRMS (EI): m /z calcd for C10 H17 NO3 : 199.1208; found: 199.1187. 14e′ : 1 H NMR (300 MHz, CDCl3 ): δ = 5.93 (br s, 1 H), 4.23 (q, J = 7.1 Hz, 2 H), 3.56 (d, J = 6.6 Hz, 1 H), 2.49 (br s, 1 H), 1.92-1.65 (m, 6 H), 1.45-1.32 (m, 3 H), 1.29 (t, J = 7.1 Hz, 3 H). 13 C NMR (75 MHz, CDCl3 ): δ = 171.3, 96.1, 70.2, 61.4, 59.5, 38.5, 32.2, 24.4, 23.5, 14.1.
14a
Baldwin SW.
Long A.
Org. Lett.
2004,
6:
1653
14b
Tamura O.
Shiro T.
Ogasawara M.
Toyao A.
Ishibashi H.
J. Org. Chem.
2005,
70:
4569