Radical methanesulfonyl

A conformational analysis of the methanesulfonyl radical indicates the staggered structure 1 as the most stable, with a barrier of rotation of ca. 3.8 kcal mol"17. The... 

Norman and coworkers21 23 used ESR spectroscopy to study in detail the reaction of several organic compounds containing the sulfinyl moiety with the Ti(III)-H202 system in particular, dimethyl sulfoxide yields the methyl and methanesulfonyl radicals as shown in reactions 1-321. 

In the reaction of 16 with methanesulfonyl bromide, a mixture of E- and Z-substituted bro-mopentenes 19 was isolated.It is probable that the radical formed by /1-scission abstracted a bromine atom from the methanesulfonyl bromide so rapidly that 1,5-hydrogen migration could not compete in this case. 

The replacement of a carboxylic acid group by nitrile functionality can also be used for the preparation of labeled compounds, and conditions for alkaline hydrolysis which did not lead to conjugation in skipped dienes like linoleic acid were developed by the Barton group. In this case, the free-radical chain sequence is straightforward, with the methanesulfonyl (or p-toluenesulfonyl) radical acting as the chain carrier [26], This methodology also represents an interesting way for the preparation of nitriles without the necessity for amide formation followed by dehydration. 

This free-radical acylation approach is extended for the synthesis of a-keto esters and ketones using phenylsulfonyl methoxycarbonyl oxime ether 5 [23] and bis-methanesulfonyl oxime ether 6, respectively (Scheme 6) [24], 5 is more reactive and effective than 2b. For instance, radical reaction of tert-butyl iodide with 5 gave tert-butyl oxime ester in 65% yield, whereas the use of 2b gave the corresponding tert-butyl oxime ether in 15% yield. In free-radical-mediated ketone synthesis via a sequential radical acylation approach, 6 is used as a carbonyl equivalent geminal radical acceptor. This method works well with primary alkyl iodides but somewhat less efficiently with secondary iodides and can be applied to prepare unsymmetrical acyclic ketones as well as cyclic ketones. It is noteworthy that stable allylic and benzylic radicals react smoothly with 6. 

Recently, Miranda and coworkers reported that tin hydride-mediated radical carbonylation can be applied to include the synthesis of ketones fused with heterocyclic rings, such as pyrroles and indoles. In the example given in run 10, an acyl radical attack at aromatic carbon and in situ oxidation leads to an indole-fused cyclopentanone in good yield [39]. On the other hand, an example shown in run 11 makes use of a methanesulfonyl group as a leaving radical [40]. When a related substrate which does not contain a sulfonyl substituent was used, a simple radical formylation took place. 

Radical addition of allyl alcohol to cyclododecanone and dehydrative cycli-sation gives a bicyclic dihydropyran. The ring-opening of the cyclic acetal of cyclododecanone with triisopropylaluminium and reclosure using trifluoro-methanesulfonyl anhydride provides an interesting alternative. The 15-hydroxy-pentadecanoic acid is then accessible by means of nitrosation, followed by Wolff-Kishner reduction. Apart from the reduction with hydrazine, catalytic, electrochemical and Clemmensen reduction are also well-established. 

Analysis of Reagent Purity H NMR, IR, elemental analysis. Preparative Methods the title reagent is prepared by the reaction of 2-(methylsulfonyl)-3-phenyl-2-propenyl alcohol and phosgene (eq 1). The alcohol is obtained from the corresponding allylic bromide by formate-catalyzed hydrolysis. The synthesis of the bromide involves the Cu(OAc)2-catalyzed addition of methanesulfonyl chloride to -methylstyrene followed by elimination of hydrogen chloride and subsequent free radical bromination of the methyl group (eq 1). ... 

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