53439-67-1Relevant academic research and scientific papers
C-S bond cleavage in the sensitized photooxygenation of tert-alkyl phenyl sulfides. The role of superoxide anion
Baciocchi, Enrico,Del Giacco, Tiziana,Giombolini, Paolo,Lanzalunga, Osvaldo
, p. 6566 - 6573 (2006)
The N-methylquinolinium tetrafluoroborate (NMQ+)-photosensitized oxidation of tert-alkyl phenyl sulfides 1a-c (1a, tert-alkyl=tert-butyl; 1b, tert-alkyl=2-phenyl-2-propyl; 1c, tert-alkyl=1,1-diphenylethyl) and benzyl phenyl sulfide (2) were investigated in CH3CN by nanosecond laser flash photolysis (LFP) and steady-state irradiation either under nitrogen or in the presence of O2. By laser irradiation, the formation of sulfide radical cations 1a+{radical dot}-c+{radical dot} in the monomeric form (λmax=520 nm) and of 2+{radical dot} in both the monomeric (λmax=520 nm) and dimeric form (λmax=780 nm) were observed within the laser pulse. In both cases, the radical cations decayed by second-order kinetics without any apparent formation of transients attributable to C-S bond rupture. In line with these results, very small amounts of photoproducts were obtained under nitrogen thus suggesting that the sulfide radical cations mainly undergo a back electron transfer process with the reduced N-methylquinolinium (NMQ{radical dot}). A different situation was found in the presence of O2 since steady-state photolysis produced substantial amounts of C-S bond cleavage products (alcohols, alkenes, and ketones from 1a-c and benzaldehyde from 2), in contrast with LFP experiments. Formation of products was, however, significantly reduced in the presence of benzoquinone, a trap for O2-{radical dot} generated by NMQ{radical dot} and O2. For the tert-alkyl phenyl sulfides, 1a-c, these results have been interpreted by suggesting that C-S bond cleavage products in the presence of oxygen mostly derive from the decomposition of a thiadioxirane 6 formed by the reaction of the sulfide radical cation with O2-{radical dot}. In this cleavage a sulfinate and a carbocation formed. The former is oxidized to sulfonate, whereas the carbocation can react with adventitious water to form the alcohol (and the alkene therefrom) and with O2-{radical dot} to produce the ketone. For 2 (a sulfide with α-CH bonds) probably a different mechanism holds, benzaldehyde coming from the α-phenylthio carbon radical formed from deprotonation by O2-{radical dot} of 2n+{radical dot}.
Nucleophilic Substitution Reaction of Cumyl Arenesulfonates with Anilines
Koh, Han Joong,Lee, Hai Whang,Lee, Ikchoon
, p. 125 - 130 (2007/10/02)
The nucleophilic substitution reaction of cumyl arenesulfonate with aniline has been investigated.The reaction in acetonitrile proceeds by the SN2 mechanism with probable frontside nucleophilic attack.The large magnitude of ρXZ (=-0.75) obtained results in an observable sign reversal of ρZ at ?'X = 0.83, with a negative ρZ value for ?X > ?'X.This rather unusual phenomenon can be rationalized by a strong interaction between the nucleophile and leaving group due to their close proximity in the transition state, which in turn is a result of the frontside nucleophilic attack.The reactions in methanol indicate that the SN1 channel competes with the SN2 pathway and ion-pair return is observed when the aniline nucleophhile concentration is low.
