Ice bath temperatures metalation a to the sulfonyl group is preferred over other possible reactions, i.e., elimination or displacement. As reported by Durst,2 however, if the solution of the metalated species is allowed to warm, to ca. -30°, rapid exothermic decomposition takes place. The decomposition products are unknown, but with -lithio methyl methanesulfonate an intractable, syrupy oil that shows strong sulfonyl bands in the ir spectrum separates from the reaction mixture. Therefore, alkylations with 1-bromopropane, and presumably with others of the less reactive alkylating agents, cannot be speeded by simply allowing the reaction mixture to warm, but, rather, the time for alkylation must be greatly extended while the reaction mixture is kept well cooled.

preparative method of orthothioborates, offers a new, simple and rapid technique of preparation of ~hioacetals, under neutral conditions. The side reactions resulting from acid catalysis, as required by the standard methods of preparation of thioacetals, can be avoided with this new procedure. Experimental I n a dry 500 ml flask, a mixture of 7.6 g (0.2 mole) of sodium borohydride and 19.2 g (0.6 mole) of sulfur was stirred with 50ml of anhydrous tetrahydrofuran (slow addition). After the initial reflux had subsided, heat was applied, for a total reflux time of 14 h. The tetrahydrofuran was then evaporated under vacuum at room temperature and 200n1l of dry petroleum ether, b.p. 30-60' was added to the hydride, with 137 g (1.8 mole) of I-propanethiol. The reaction mixture was then refluxed overnight.The crude mixture was then filtered on a carefully dried sintered glass filter (medium porosity). It is advantageous to keep the system dry during the filtration, using a stream of dry nitrogen flowing through an inverted funnel over the filter. After evaporation of the solvent at atmospheric pressure under dry nitrogen, the residue (56.0 g) was then fractionated under vacuum. The first fraction was di-n-propyl disulfide, 20. In a dry 250 n~l flask, 6.7 g (0.93 mole) of butanone were mixed with 16.1 g (0.82 mole) of ethyl orthoborate. Upon warming, the mixture assumed a gel-like appearance. After a lh-contact, the mass was extracted with petroleum ether. The boric anhydride was filtered off, the solvent evaporated, and the crude thioacetal distilled. The main fraction was the ethyl thioacetal of butanone, b.p. 73"/0.15 mm, nDZ8 1.4959. Reported (2) Strong bases affect 3-metallation of alkyl alkanesulfonates; subsequent alk~lation offers a useful approach to esters of ;he higher sulfonic acids.

No abstract

Page 2863. Column 2, line 11. "exothermic" should read "endothermic." Page 2864. Column 1, line 10. Reference 23 (superscript) should read 2 (superscript).

Alkansulfonsäureester (I) werden durch Behandlung mit Butyllithium und Alkylierungsmitteln (III) über die Zwischenstufen (II) zu (IV) alkyliert.