Dimethyl sulphide procedure

A most convenient procedure for the conversion of carboxylic acids to aldehydes results from their initial treatment with borane-dimethyl sulphide to give first, the triacyloxyborane (9), which is then reduced further to the intermediate (10) the trimer of (10) is the trialkyloxyboroxine (11). Oxidation of (11) with PCC then yields the aldehyde.110 The method is illustrated for the preparation of octanal (Expt 5.81), but it has been applied to cyclohexanecarboxylic acid and to various aromatic carboxylic acids (X-C6H4C02H, X = p-Cl, NOz, OMe, ni-CN). 

Kettle AJ et al (1999) A global database of sea surface dimethyl sulphide (DMS) measurements and a procedure to predict sea surface DMS as a function of latitude, longitude and month. Global Biogeochem Cycles 13 399-444... 

Additions of organometallic reagents to 1-alkynes continue to play a prominent role in the regio- and stereo-selective synthesis of olefins. A convenient procedure for the stereospecific synthesis of trisubstituted olefins, based on Normant s work on the addition of alkyl copper(l) complexes to 1-alkynes, is outlined in Scheme 10. The use of House s dimethyl sulphide-copper(i) bromide complex minimizes... 

Dodecane-l,12- C has been synthesized by the procedure shown in equation 32. 1,10-Dibromodecane treated with cyanide- in aqueous ethanoF gave the dinitrile which was hydrolyzed in situ to the acid, 20, and in turn reduced with a borane-dimethyl sulphide complex to l,12-dodecanediol-l,12- C in 90% yield. The bis-tosylate of 20 has then been reduced to the required dodecane (1,12- C) in 30% yield, enriched with up to 88.9%. 

Restricted Internal Rotation of Several Symmetric Tops. The tables of thermodynamic functions for an internal rotation of a single symmetric top may be used for several symmetric tops [with moments of inertia calculated from equation (20)] provided both potential energy and kinetic energy cross-terms between the tops can be neglected. Both assumptions have been generally made in calculations for molecules with several tops. Where there are reliable calorimetric data at one or more temperatures, the tables have been used to calculate appropriate potential barriers. Using this procedure thermodynamic contributions have been calculated for propane, 2-methylpropane, 2,2-dimethylpropane, cis-but-2-ene, rm a -but-2-ene, isobutene, o-xylene, > m-xylene, p-xylene, 1,2,3-trimethylbenzene, > 1,2,4-trimethylbenzene, dimethyl sulphide,2-chloro-2-methylpropane, and dimethyl-amine. In several cases thermodynamic contributions have been calculated using potential barriers estimated from those of related molecules. Examples of this procedure are found in calculations for 2-fluoro-2-methylpropane, 2-chloropropane, 2-bromopropane, 2-iodopro-pane, 2,2-dichloropropane, 2-bromo-2-methylpropane, 2-iodo-2-methylpropane, 1,3,5-trimethylbenzene, 1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, 1,2,3,4-tetramethylbenzene, pentamethyl-benzene, and hexamethylbenzene. ... 

Improved procedures for the reduction of amides, and nitriles to the corresponding amines have been reported. The requirement of no more borane reagent than the calculated quantity for the borane-dimethyl sulphide reduction of primary amides is a consequence of distilling dimethyl sulphide out of the reaction mixture (Scheme 2), and represents a significant improvement in... 

Reduction of Carbonyl Groups. Rapid reduction of salts of carboxylic acids to alcohols with 2 molar equivalents of borane in tetrahydrofuran (THF) has been reported. Full details have appeared of the improved procedure for reduction of esters to primary alcohols, using borane dimethyl sulphide (6,157) in THF at reflux, which allows the dimethyl sulphide that is liberated to distil off during the reaction. Further suggested procedures for the reduction of esters to primary alcohols use lithium borohydride in diethyl ether or THF, calcium borohydride in THF, and sodium borohydride in a t-butyl alcohol-methanol mixed solvent. The reactions using lithium borohydride-diethyl ether can be catalysed by lithium 9-boratobicyclo[3.3.1]nonane (1), lithium triethylboro-hydride, or the Lewis acid 9-methoxy-9-borabicyclo[3.3.1]nonane (2). ... 

Helquist and his co-workers find that the dimethyl sulphide-copper(i) bromide complex with methylmagnesium bromide will add to simple terminal acetylenes in stoicheiometric amounts, or in only a small excess (10—15%) this procedure allows a more efficient means of constructing stereochemically defined methyl trisubstituted olefins found in natural isoprenoids (Scheme 10). 

Both inorganic and organic hypochlorites may be used for the oxidation of sulphoxides. The cheapest method involves the use of a commercial bleach, such as Chlorox . Such a method is indeed successful for unsaturated sulphoxides such as allyl methyl sulphoxide although the yields are generally low. Other sulphoxides may also be oxidized by this method, for example, dimethyl sulphoxide gave bis(trichloromethyl) sulphone in low yield . In some cases bis(dichloromethyl) sulphone was also isolated in very low yield. This oxidation procedure is also commonly used by organosulphur chemists for the removal of unwanted odours, caused by sulphoxides (and sulphides), from dirty glassware. 

Many applications of Kilpatrick and Pitzer s procedure for calculating thermodynamic properties of molecules with compound rotation have been reported. In all cases possible potential energy cross-terms between rotating tops have been neglected. Contributions from internal rotation of symmetric tops have been calculated using the appropriate tables." These tables have also been used in calculations for the internal rotation of asymmetric tops hindered by a simple -fold cosine potential. 3-Fold potential barriers have been assumed in calculations for the —OH rotations in propanol and 1-methylpropanol, the —SH rotations in propane-1-thiol, butane-2-thiol, 2-methylpropane-l-thiol, and 2-methylbutane-2-thiol, the C—S skeletal rotations in ethyl methyl sulphide, diethyl sulphide, isopropyl methyl sulphide, and t-butyl methyl sulphide, and the C—C skeletal rotations in 2,3-dimethylbutane, and 2-methylpropane-l-thiol. 2-Fold cosine potential barriers have been assumed in calculations in the S—S skeletal rotations in dimethyl disulphide and diethyl disulphide. ... 

Keto esters.—Acylimidazolides react readily with Grignard reagents to provide a general method for the synthesis of a-keto-esters yields are variable over a series of 11 examples. /3-hydroxy-esters and ketones, obtained by the aldol condensation, have been oxidized to /3-keto-esters and ketones most efficiently by the Swern procedure using dimethyl sulphoxide and oxalyl chloride. Sulphide contraction of thiopyrrolidines has been shown to be an effective synthesis of /3-keto-esters and nitriles (Scheme 42). ... 

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