Synlett 2007(1): 0083-0086  
DOI: 10.1055/s-2006-958441
LETTER
© Georg Thieme Verlag Stuttgart · New York

Diastereoselective Passerini Reaction of Chiral 2,3-Epoxy Aldehydes with TosMIC [1]

Palakodety Radha Krishna*, Krishnarao Lopinti
D-206/B, Discovery Laboratory, Organic Chemistry Division-III, Indian Institute of Chemical Technology, Hyderabad 500007, India
e-Mail: prkgenius@iict.res.in;
Further Information

Publication History

Received 27 June 2006
Publication Date:
20 December 2006 (online)

Abstract

A diastereoselective three-component Passerini reaction (P-3CR) of chiral 2,3-epoxy aldehydes with tosylmethyl isocyanide (TosMIC) under benzoic acid conditions to afford densely substituted products in moderate to good yields and diastereomeric excess is reported.

1

IICT Communication number: 060606.

1

IICT Communication number: 060606.

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The authors are thankful to the referee who has suggested conducting the Passerini reaction in presence of chiral acids.

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General Experimental Procedure.
To a stirred solution of the epoxy aldehyde (1.16 mmol) in CH2Cl2 (4 mL) was added benzoic acid (1.16 mmol) and TosMIC (1.04 mmol) at r.t. The reaction mixture was stirred for 48 h at the same temperature. After complete consumption of TosMIC, CH2Cl2 was removed to obtain a residue, which was purified by column chromatography (silica gel, 60-120 mesh, EtOAc-n-hexane, 8.5:1.5) to afford products 1a-9a in 50-79% yields.

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Spectral Data of Selected Compounds. Compound 1a: 1H NMR (300 MHz, CDCl3): δ = 8.08 (d, 2 H, J = 6.80 Hz, ArH), 8.06 (d, 1 H, J = 4.90 Hz, ArH), 7.76 (d, 1.6 H, J = 7.90 Hz, ArH), 7.70 (d, 0.4 H, J = 8.30 Hz, ArH), 7.58 (d, 1 H, J = 6.80 Hz, ArH), 7.48-7.40 (m, 4 H, NH, ArH), 7.25 (d, 5 H, J = 5.70 Hz, ArH), 5.15 (d, 0.2 H, J = 6.90 Hz, OCH), 5.10 (d, 0.8 H, J = 7.90 Hz, OCH), 4.69-4.46 (m, 4 H, NCH2, benzylic CH2), 3.83 (d, 0.4 H, J = 4.90 Hz, OCH2), 3.76 (d, 1.6 H, J = 4.50 Hz, OCH2), 3.33-3.15 (m, 2 H, epoxide CH2), 2.40 (s, 0.6 H, CH3), 2.38 (s, 2.4 H, CH3). IR (KBr): 3360, 2932, 2857, 1712, 1622, 1520, 1330 cm-1. MS (ES): m/z (%) = 510 (28) [M + 1]. Anal. Calcd (%) for C27H27NO7S: C, 63.64; H, 5.34. Found: C, 63.63; H, 5.36.
Compound 3a: 1H NMR (200 MHz, CDCl3): δ = 8.12-8.07 (m, 3 H, ArH), 7.61 (d, 2 H, J = 6.94 Hz, ArH), 7.57 (d, 1 H, J = 7.81 Hz, ArH), 7.51-7.43 (m, 3 H, NH, ArH), 7.36-7.27 (m, 1 H, ArH), 5.42 (d, 0.85 H, J = 3.50 Hz, OCH), 5.24 (d, 0.15 H, J = 5.20 Hz, OCH), 4.68 (d, 2 H, J = 8.70 Hz, NCH2), 4.13-4.02 (m, 2 H, OCH2), 3.83-3.79 (m, 1 H, OCH), 3.33-3.30 (m, 1 H, epoxy-H), 3.12-2.92 (m, 1 H, epoxy-H), 2.45 (br s, 3 H, CH3), 1.42-1.31 (m, 6 H, acetonide). IR (KBr): 3377, 2925, 2855, 1713, 1598, 1526, 1379 cm-1. MS (ES): m/z (%) = 508 (35) [M+ + Na]. Anal. Calcd (%) for C24H27NO8S: C, 58.88; H, 5.56. Found: C, 58.77; H, 5.51.
Compound 4a: 1H NMR (300 MHz, CDCl3): δ = 8.12 (d, 2.5 H, J = 7.60 Hz, ArH), 8.07 (d, 0.5 H, J = 7.90 Hz, ArH), 7.74 (d, 1 H, J = 7.93 Hz, ArH), 7.61-7.53 (m, 2 H, ArH), 7.48-7.40 (m, 3 H, NH, ArH), 7.30 (d, 1 H, J = 7.93 Hz, ArH), 5.16 (d, 0.17 H, J = 7.55 Hz, OCH), 5.14 (d, 0.83 H, J = 9.44 Hz, OCH), 4.78-4.69 (m, 1 H, NCH2), 4.54-4.47 (m, 1 H, NCH2), 4.36-4.30 (m, 1 H, OCH), 4.10 (d, 2 H, J = 5.70 Hz, OCH2), 3.32-3.29 (m, 0.34 H, epoxy-H), 3.23-3.15 (m, 1.66 H, epoxy-H), 2.59 (br s, 0.5 H, CH3), 2.49 (s, 2.5 H, CH3), 1.50 (d, 3 H, J = 17.5 Hz, acetonide), 1.30-1.24 (m, 3 H, acetonide). IR (KBr): 3376, 2922, 2857, 1719, 1588, 1520, 1369 cm-1. MS (ES): m/z (%) = 508 (32) [M+ + Na]. Anal. Calcd (%) for C24H27NO8S: C, 58.88; H, 5.56. Found: C, 58.79; H, 5.47.
Compound 5a: 1H NMR (200 MHz, CDCl3): δ = 8.05 (d, 2 H, J = 7.00 Hz, ArH), 7.70 (d, 2 H, J = 8.60 Hz, ArH), 7.55 (d, 1 H, J = 7.00 Hz, ArH), 7.44 (d, 1.5 H, J = 7.80 Hz, ArH), 7.03 (d, 0.5 H, J = 7.00 Hz, ArH), 7.27-7.20 (m, 8 H, NH, ArH), 5.23 (d, 0.75 H, J = 3.90 Hz, OCH), 5.15 (d, 0.25 H, J = 5.50 Hz, OCH), 4.64-4.59 (m, 2 H, NCH2), 4.46 (s, 2 H, CH 2Ph), 3.46-3.43 (m, 2 H, OCH2), 3.04-2.94 (m, 2 H, epoxy-H), 2.39 (s, 3 H, CH3), 1.71-1.60 (m, 4 H, CH2). IR (KBr): 3354, 3065, 2924, 2854, 1690, 1601, 1526, 1452 cm-1. MS (ES): m/z (%) = 533 (27) [M + H]. Anal. Calcd (%) for C29H31NO7S: C, 64.79; H, 5.81. Found: C, 64.71; H, 5.79.
Compound 6a: 1H NMR (200 MHz, CDCl3): δ = 8.07 (d, 3 H, J = 6.80 Hz, ArH), 7.63-7.56 (m, 1 H, ArH), 7.46-7.39 (m, 4 H, NH, ArH), 7.28-7.25 (m, 7 H, ArH), 5.32 (d, 0.27 H, J = 4.20 Hz, OCH), 5.24 (d, 0.73 H, J = 5.70 Hz, OCH), 4.66-4.60 (m, 2 H, NCH2), 4.46 (s, 2 H, CH 2Ph), 3.48-3.44 (m, 2 H, OCH2), 3.08-2.94 (m, 2 H, epoxy-H), 2.38 (s, 3 H, CH3), 1.69-1.58 (m, 4 H, CH2). IR (KBr): 3356, 3061, 2925, 2862, 1692, 1621, 1526, 1458 cm-1. MS (ES): m/z (%) = 533 (28) [M + H]. Anal. Calcd (%) for C29H31NO7S: C, 64.79; H, 5.81. Found: C, 64.71; H, 5.77.