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

Abstract

The reaction of chloromethyl ethynyl sulfide with Bu 2 SnH 2 /LDA affords 2,3-dibutyl-2,3-dihydro-1,3-thiastannole which on reaction with AsBr 3 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 Me 2 SnCl 2 affords an 80% yield of 2,3-dihydro-2,2-dimethyl-1,2-thiastannole which on reaction with AsBr 3 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 (∠ R /deg) with estimated 2σ uncertainties are r(C-H) ) 1.078( 14), r(C 3 -C 4 ) ) 1.414(10), r(C 4 -C 5 ) ) 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.

Aromaticity of Phosphorus Heterocycles

“…The 1,2-thiaphosphole exhibits smaller values than the 1,3-derivative, similar to the azaphospholes . It is worth mentioning that very recently the unsubstituted 1,2- and 1,3-thiaarsoles were also reported …”

“…41 It is worth mentioning that very recently the unsubstituted 1,2and 1,3-thiaarsoles were also reported. 58 Among thiadiphospholes, the 1,2,4-and 1,3,4thiadiphospholes were reported recently by reacting t BuCP with CS 2 (or with an ylidic derivative of carbon disulfide). 59 The HF/6-311+G(d,p)//B3LYP/6-311+ G(d,p) NICS(0) values for the 1,2,4-and 1,3,4-thiadiphospholes were -12.4 and -12.7, respectively, matching favorably with the -13.2 value obtained for thiophene.…”

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“…An electron diffraction study of the former is consistent with it being aromatic. 98 Thermolysis of the arsenidene complex [Cp * As{W(CO) 5 } 2 ] gave 99 a number of compounds including [W(CO) 2 (h 3 -As 3 )Cp * ] and [{W(CO) 3 Cp * W} 2 (m 3 -As) 4 ]. The reactions involve Cp * migration from arsenic to tungsten and are believed to proceed via intermediates containing W•As triple bonds.…”

1,2-Benzothiaborolide: A New Heteroaromatic Analogue of Indenyl

“…Reaction of 8 with Bu 2 SnCl 2 gives 2,2-dibutyl-2,3-dihydro-1,2-benzothiastannole ( 9 ) in 63% yield 8b. Since similar organotin compounds undergo facile exchange reactions with main-group-element halides, − 9 may be useful for the syntheses of other sulfur heterocycles.

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