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Synlett 2008(5): 659-662  
DOI: 10.1055/s-2008-1032105
LETTER
© Georg Thieme Verlag Stuttgart · New York

Microwave-Assisted Reactions of α-Diazosulfoxides to Form α-Oxosulfines

Orlagh C. M. O’Sullivan, Stuart G. Collins, Anita R. Maguire
Department of Chemistry, Analytical and Biological Chemistry Research Facility, University College Cork, Ireland
Fax: +353(21)4274097; e-Mail: a.maguire@ucc.ie;
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Publication History

Received 11 October 2007
Publication Date:
26 February 2008 (online)

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Microwave-Assisted Reactions of α-Diazosulfoxides to Form α-OxosulfinesSynlett 2008; 2008(05): e2-e2
DOI: 10.1055/s-2008-1066989

Abstract

Wolff rearrangement of α-diazosulfoxides has been induced by microwave irradiation forming α-oxosulfines. The outcome of the transformation was similar to the outcome under thermal conditions, with no evidence of specific microwave effects. Critically, this methodology allows generation of these synthetically useful α-oxosulfines in the absence of a transition-metal catalyst. Confirmation of the stereochemistry of the α-oxosulfines was undertaken by trapping as Diels-Alder cycloadducts indicating that the (Z)-oxosulfines are the kinetic products but rearrange to the thermodynamically favoured (E)-oxosulfines in the absence of a diene trap during their formation.

Key words

diazosulfoxides - microwave-assisted reactions - Wolff rearrangement - sulfine - Diels-Alder cycloadditions

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Collins, S. G. Maguire, A. R. unpublished results

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General Experimental ProcedureThe diazosulfoxide (20 mg, 1 equiv) and 2,3-dimethyl-1,3-butadiene (10 equiv) were dissolved in distilled CH2Cl2 (2 mL) in a sealed 10 mL microwave vessel. A CEM Discover microwave was employed to irradiate the reaction mixtures to 135 °C using a 3 min ramp and 7 min hold time. Reaction temperature was recorded using an IR sensor. The solvent was removed in vacuo and NMR spectra of the residues were recorded and used to obtain the ratio of cycloadducts formed in each experiment. Representative Spectral DataCycloadduct 6: mp 164-166 °C. Anal. Calcd (%) for C14H20O3S: C, 62.66; H, 7.51. Found: C, 62.67; H, 7.48. IR (KBr): νmax = 1765 (C=O), 1023 (S=O) cm-1. 1H NMR (300.13 MHz, CDCl3): δ = 1.15-2.17 (13 H, m, cyclohexyl ring and s at 1.73 for Me groups), 2.24-2.39 (1 H, m, cyclohexyl ring), 2.48 (1 H, A of ABq, J = 17.7 Hz, one of allylic CH2 ), 2.59-2.76 (2 H, m including B of ABq, bridgehead CHC and one of allylic CH2), 3.23 (1 H, A of ABq, J = 16.4 Hz, one of SOCH2), 3.76 (1 H, B of ABq, J = 16.6 Hz, one of SOCH2), 4.00 (1 H, overlapping ddd appears as td, J = 11.1, 11.1, 3.7, CHO) 13C NMR (75.5 MHz, CDCl3): δ = 18.5, 18.8 (2 × CH2, Me groups), 22.6, 24.2, 25.4, 29.4 (4 × CH2, cyclohexyl ring), 29.4 (CH2, allylic CH2), 43.9 (CH, bridgehead CHC), 50.3 (CH2, SOCH2), 63.1 (q, CS), 50.3 (CH, bridgehead CHO), 117.5 (q, C=C), 124.0 (q, C=C), 172.8 (q, C=O).Cycloadduct 7: mp 178-180 °C. IR (KBr): νmax = 1768 (C=O), 1038 (S=O) cm-1. 1H NMR (300.13 MHz, CDCl3): δ = 1.21-2.31 (15 H, m including two s at 1.66 and 1.76, cyclohexyl ring, bridgehead CHC and Me groups), 2.40 (2 H, s, allylic CH2), 3.54 (1 H, A of ABq, J = 15.1 Hz, one of SOCH2), 3.94 (1 H, B of ABq, J = 15.1 Hz, one of SOCH2), 4.56 (1 H, td, J = 10.9, 3.8, bridgehead CHO). 13C NMR (75.5 MHz, CDCl3): δ = 18.9, 20.0 (2 × CH3, Me groups) 23.4, 23.6, 25.5, 31.1, 38.6 (5 × CH2, cyclohexyl ring and allylic CH2), 51.6 (CH2, SOCH2), 54.5 (CH, bridgehead CHC), 63.6 (q, CS), 81.6 (CH, bridgehead CHO), 118.4 (q, C=C), 126.2 (q, C=C), 173.3 (q, C=O). HRMS (ESI+): m/z C14H21O3S [M + H]+: 269.1211; found: 269.1223.

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Diazosulfoxides 2 and 3 were reacted in diastereomerically pure form as illustrated in Scheme 1 and also as a mixture of diastereomers at sulfur with essentially the same results.