Organoboranes. 35. Reaction of Alkylthioboronic Esters with Trichloromethyllithium: Preparation of One-Carbon-Extended Carboxylic Acids and Thioacetals from Alkenes via Hydroboration

Article abstract of DOI:10.1021/jo00179a027

Various 2-alkyl-1,3,2-dithiaborolanes, RB(S2C2H4) (1), were converted to the corresponding carboxylic acids, RCO2H (2), by using LiCCl3 in THF, followed by oxidation with alkaline hydrogen peroxide.For R=hexyl, a reaction intermediate is converted by solvent into another compound, C6H13C(S2C2H4)B2 (9a), characterized spectroscopically.The yields of 2 decreased with increasing bulkiness of the alkyl groups R.Although the configuration of R= trans-2-methylcyclopent-1-yl (1k) was retained in the product (>98percent trans), a significant degree of epimerization tookplace for R= exo-norbornyl (1j) during the oxidation (exo : endo = 86 : 14).More uniquely, the intermediates 9 were easily hydrolyzed by heating the reaction mixture with aqueous NaOH to give the corresponding 2-alkyl-1,3-dithiolanes 3.Stereochemical integrity was retained in the products derived from 1j and 1k.Since 1 was prepared by the hydroboration of alkenes, this sequence provides a new method for introducing oxycarbonyl or thioacetal functionality into alkenes in a regioselective manner, and, in the case of 3, also with stereocontrol.

Full text of DOI:10.1021/jo00179a027

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.