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Synlett 2011(11): 1533-1536  
DOI: 10.1055/s-0030-1260772
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Weinreb Amide Based Building Blocks for the Synthesis of α- and β-Organylseleno Aryl Ketones

Sivaraman Balasubramaniam, Indrapal Singh Aidhen*
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India
Fax: +91(44)22574202; e-Mail: isingh@iitm.ac.in;
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Publication History

Received 24 March 2011
Publication Date:
15 June 2011 (online)

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Abstract

A new strategy for the synthesis of α- and β-organylseleno aryl ketones has been achieved. The strategy is based on the use of hitherto unreported 2,2′-diselenediylbis(N-methoxy-N-methyl­acetamide) and 3,3′-diselenediylbis(N-methoxy-N-methylpropan­amide). The envisaged synthetic equivalents combine the usefulness of Weinreb amide (WA) functionality and those innate with selenium for the first time. The synthesis of the targets, α- and β-organylseleno aryl ketones could be achieved by the reductive cleavage of Se-Se bond, followed by the alkylation on selenium, and the addition of arylmagnesium halide onto the WA functionality therein.

Key words

Weinreb amide - reductive alkylation - glycosylseleno ketones - Grignard addition

14

2,2′-Diselenediylbis( N -methoxy- N -methylacetamide) (4) Yield 45%. R f = 0.20 (hexanes-EtOAc = 6:4), yellow colored liquid. ¹H NMR (400 MHz, CDCl3): δ = 3.14 (s, 3 H, NCH3), 3.52 (s, 2 H, SeCH2), 3.68 (s, 3 H, OCH3). ¹³C NMR (100 MHz, CDCl3): δ = 29.6, 32.5, 61.5, 171.2. IR (CHCl3): 2929, 2850, 1637, 1445, 1155 cm-¹. ESI-HRMS: m/z calcd for C8H16N2O4NaSe2 [M + Na]+: 386.9338; found: 386.9344.
3,3′-Diselenediylbis( N -methoxy- N -methylpropan-amide) (5)
Yield 65%. R f =0.25 (hexanes-EtOAc = 6:4), yellow colored liquid. ¹H NMR (400 MHz, CDCl3): δ = 2.94-2.98 (m, 2 H, COCH2), 3.12-3.15 (m, 2 H, SeCH2), 3.19 (s, 3 H, NCH3), 3.70 (s, 3 H, OCH3). ¹³C NMR (100 MHz, CDCl3): δ = 22.1, 29.1, 32.4, 61.5, 171.5. IR (CHCl3): 2921, 2847, 1626, 1458, 1166 cm-¹. ESI-HRMS: m/z calcd for C10H21N2O4Se2 [M + H]+: 392.9832; found: 392.9833.

15

The sugar halides 13 and 14 were prepared through multistep reaction sequence from commercially available monosacchride d-(+)-glucono-1,5-lactone.