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Synlett 2010(16): 2453-2456  
DOI: 10.1055/s-0030-1258056
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Practical and Highly Efficient Hydroacylation Reaction of Azodicarboxylates with Aldehydes in Water

Qianying Zhang, Erica Parker, Allan D. Headley*, Bukuo Ni*
Department of Chemistry, Texas A&M University-Commerce, Commerce, TX 75429-3011, USA
Fax: +1(903)4686020; e-Mail: allan_headley@tamu-commerce.edu; e-Mail: bukuo_ni@tamu-commerce.edu;
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Publication History

Received 10 May 2010
Publication Date:
19 August 2010 (online)

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Abstract

The very efficient hydroacylation reaction of azodicarboxylates, with various aldehydes, was carried successfully out at room temperature in water without the use of a catalyst to obtain a variety of hydrazine imide products in high yields. A wide range of aldehydes, including aliphatic and aromatic compounds, was considered, and the reaction is believed to proceed via a radical mechanism, in which water plays an integral role in stabilizing the radical intermediate.

Key words

azo compounds - green chemistry - hydroacylation - aldehydes

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The reaction of hexanal and diisopropyl azodicarboxylate without catalyst under neat conditions was described by Lee et al.¹0a and afforded the addition product with 14 days at r.t.

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Due to the many byproducts observed in the reaction mixture, the bisazodicarboxylates could not be isolated.¹0a

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Typical Procedure for the Hydroacylation Reaction in H 2 O
To a stirred solution of aldehyde 1 (1.0 mmol) in H2O (0.5 mL) was added azodicarboxylate 2 (0.5 mmol). The reaction was stirred at r.t. for the time as indicated in Tables  [¹] and  [²] . The reaction mixture was extracted with Et2O for two times (4 × 5 mL). The Et2O solution was combined, concentrated, and purified by flash chromatography on silica gel (hexane-EtOAc = 4:1) to afford the product 3.
Data for the new hydroacylation products: Compound 3b: ¹H NMR (400 MHz, CDCl3): δ = 6.57 (br, 1 H), 5.10-4.90 (m, 2 H), 2.94-2.84 (m, 2 H), 1.72-1.58 (m, 4 H), 1.40-1.15 (m, 20 H), 0.88 (t, J = 6.8 Hz, 3 H) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 173.9, 155.1, 152.6, 72.1, 70.4, 37.0, 31.8, 29.3, 29.2, 29.1, 24.7, 24.6, 22.6, 21.9, 21.7, 14.1 ppm. Anal. Calcd for C16H32N2O5Na [M + Na]+: 367.2209; found: 367.2207. Compound 3n: ¹H NMR (400 MHz, CDCl3): δ = 6.68 (br, 1 H), 4.30 (q, J = 7.2 Hz, 2 H), 4.21 (q, J = 7.2 Hz, 2 H), 3.44-3.34 (m, 1 H), 2.00-1.60 (m, 6 H), 1.52-1.17 (m, 10 H) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 177.1, 155.6, 153.1, 63.7, 62.4, 62.2, 43.9, 29.3, 28.9, 28.8, 25.7, 25.6, 25.5, 25.3, 14.3, 14.1 ppm. Anal. Calcd for C13H22N2O5Na [M + Na]+: 309.1421; found: 309.1421. Compound 3o: ¹H NMR (400 MHz, CDCl3): δ = 7.34 (br, 10 H), 6.76 (br, 1 H), 5.24 (s, 2 H), 5.17 (s, 2 H), 3.46-3.26 (m, 1 H), 2.00-1.14 (m, 10 H) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 176.8, 155.4, 153.0, 135.3, 134.7, 128.6, 128.5, 128.4, 128.1, 69.1, 68.0, 43.9, 29.3, 28.8, 25.7, 25.5, 25.3 ppm. Anal. Calcd for C23H26N2O5Na [M + Na]+: 433.1734; found: 433.1738.