PART I: THE SYNTHESIS OF CIS-1,2-BIS(PARA- TOLYLSULFONYL)CYCLOPENTANE. PART II: MECHANISTIC STUDIES OF THE BASE-INDUCED COUPLING-CONDENSATION OF ARYL ORTHO- AND PARA- METHYLARENESULFONATES AND ORTHO- AND PARA- METHYLARENE SULFONANILIDES

JING-JONG LU, Purdue University

Abstract

Part I. Several synthetic approaches to cis-1,2-bis(p-tolylmercapto)cyclopentane have been studied. (I) Nucleophilic substitution by p-toluenethiolate upon trans-1-p-tolylmercapto-2-chlorocyclopentane formed trans-1,2-bis(p-tolylmercapto)cyclopentane. (II)(FDIAG)sThe addition of p-toluenesulfenyl chloride to 1-p-tolylmercaptocyclopentene, followed by reduction with sodium borohydride gave 10% of the expected product, cis-1,2-bis(p-tolylmercapto)cyclopentane in addition to 71% of bis(p-tolylmercapto)methane. (III) The radical chain-addition of p-toluenethiol to 1-p-tolylmercaptocyclopentene resulted in the formation primarily of cis-1,2-bis(p-tolylmercapto)cyclopentane along with a small amount of its trans-isomer. (IV) Attempted reductions of 1,2-bis(p-tolylmercapto)cyclopentene were unsuccessful. Consideration was also given to several synthetic approaches to cis-1-p-tolylsulfonyl-2-p-tolylmercaptocyclopentane. (I) Nucleophilic substitution by p-toluenethiolate upon trans-1-p-tolylsulfonyl-2-chlorocyclopentane formed the expected product, cis-1-p-tolylsulfonyl-2-p-tolylmercaptocylcopentane and its trans-isomer via S(,N)2 displacement and elimination-addition sequences. (II) The addition of p-toluenesulfenyl chloride to 1-p-tolylsulfonylcyclopentene, followed by reduction with sodium borohydride gave trans-1-p-tolylsulfonyl-2-p-tolylmercaptocyclopentane. (III) The attempted radical chain-additon of p-toluenethiol to 1-p-tolylsulfonylcyclopentene was unsuccessful. cis-1,2-Bis(p-tolylsulfonyl)cyclopentane was readily prepared by the oxidation of cis-1,2-bis(p-tolylmercapto)-cyclopentane or cis-1-p-tolylsulfonyl-2-p-tolylmercaptocyclopentane with hydrogen peroxide and it was also readily isomerized to its trans-isomer by treatment with sodium methoxide at room temperature. Part II. Determination of the mechanism of the n-butyllithium-induced coupling-condensation reaction of aryl o- and p-methylarenesulfonates and o- and p-methylarenesulfonanilides has been approached by studying: (I) the rate of the formation of the coupling-condensation products, (II) the crossing-condensation reaction, (III) the epr spectra of a radical intermediate and its spin adduct, (IV) the effect of light, tert-nitrosobutane, tert-nitrobutane, sodium and sodium naphthalenide on the reaction. Four possible radical mechanisms are proposed. On the basis of experimental results and logical postulation, the mechanism which involves initial fragmentation of the metalated sulfonyl substrate into a radical and a radical-anion seems to be the most reasonable pathway for the coupling-condensation reaction. Attempts to extend the scope of the reaction to additional classes of substrates such as o-methylarene-sulfonanilides of primary arylamines, secondary dialkylamines, o-ethylarenesulfonamides of secondary arylamines and aryl m-methylarenesulfonates were unsuccessful. However, the base-induced coupling-condensation of aryl o-methylarenesulfonates and o-methylarenesulfonanilides could be extended to p-methyl compounds such as N-methyl-N-phenyl-p-toluenesulfonamide and phenyl p-toluenesulfonate by using lithium diisopropylamide as a base instead of n-butyllithium.

Degree

Ph.D.

Subject Area

Organic chemistry

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