1,5-Cyclooctanediylboryl sulfides

Bis(l,5-cyclooctanediylboryl)sulfide is a white crystalline solid, which melts at 104-105° without decomposition and can be sublimed in vacuo (0.001 torr, bath 85-110°). The compound must be stored with strict exclusion of moisture and air. The sulfide is very soluble in aliphatic and aromatic hydrocarbons such as toluene or mesitylene and can be crystallized from heptane at very low temperatures. 

Thiocarboxylic acid borylesters 73 have been prepared by thioboration of the corresponding esters with bis(l,5-cyclooctanediylboryl) sulfide [185]. Treatment of [B3Hy]2 or B3H7/THF with thioacetic acid has been shown to lead to acylthiotriborane 74 [18]. 

Other boryl esters of dithiocarboxylic acids 69 are obtained by sulfurization of the corresponding carboxylic acids, esters or amides with organoboron sulfides such as (9-BBN)2S andbis(l,5-cyclooctanediylboryl) sulfide (Scheme 16) [124,125]. Methanolysis of the boryl esters 69 gives the corresponding dithiocarboxylic acids. 

A number of organoboron chalcogen compounds formed between the 1,5-cyclooctanediylboryl residue(s) and the chalcogenides sulfide and selenide,... 

The described reactions start from the compounds bis-9-bora-bicyclo[3.3.1]nonane (9H-9-BBN)2, elemental sulfur (Sg), and dihydrogen sulfide or from the easily preparable 9-iodo-9-borabicyclo[3.3.1]nonane. The procedures are simple and practicable, and the yields are nearly quantitative. The (9H-9-BBN)2-sulfur reaction can be followed not only by NMR spectroscopy but also by volumetric measurements of the evolved gas (H2). It is also remarkable that the BC bonds of the 1,5-cyclooctanediylboryl group are completely stable toward sulfidation at temperatures up to about 150 . The three compounds described here can be prepared easily on a scale of some 100 g of high purity. If necessary, the purification is possible, involving distillation or sublimation under vacuum without any decomposition. 

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