Aromatic Heterocycles Containing Arsenic and Sulfur:  The Synthesis of 1,2- and 1,3-Thiaarsole and the Gas-Phase Molecular Structure of 1,2-Thiaarsole

• Published in: Journal of the American Chemical Society 2000-07, Vol.122 (29), p.7012-7016
• Main Authors: Ashe, Arthur J, Fang, Xinggao, Schiesher, Matthew, Richardson, Alan D, Hedberg, Kenneth
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja993924z

The reaction of chloromethyl ethynyl sulfide with Bu2SnH2/LDA affords 2,3-dibutyl-2,3-dihydro-1,3-thiastannole which on reaction with AsBr3 followed by DBU affords 1,3-thiaarsole in 22% yield. The reaction of allyl mercaptan with 2 equiv of BuLi followed by 1 equiv of Me2SnCl2 affords an 80% yield of 2,3-dihydro-2,2-dimethyl-1,2-thiastannole which on reaction with AsBr3 followed by DBU gives 1,2-thiaarsole in 56% yield. The NMR, UV and mass spectra are consistent with aromaticity of both thiaarsoles. The structure of 1,2-thiaarsole, measured by electron diffraction, suggests that it is an aromatic compound. The thermal average bond lengths (r g/Å) and bond angles (∠α/deg) with estimated 2σ uncertainties are r(C−H) = 1.078(14), r(C3−C4) = 1.414(10), r(C4−C5) = 1.382(9), r(As−C) = 1.829(4), r(S−C) = 1.711(5), ∠(CCC) = 118.0(12), ∠(AsCC) = 117.7(10), ∠(SCC) = 117.9(9), ∠(SAsC) = 89.8(5), ∠(AsSC) = 96.6(4). Ab initio molecular orbital calculations at the B3LYP/6-31G* level were performed for both thiaarsoles.