Sulfoxide centers, displacements

An analogous free radical displacement reaction is observed at sulfoxide centers, but fails for the corresponding sulfone. Thus, photolysis of methyl 2-(o-iodophenyl)ethyl sulfoxide (X, R=CH3) in cyclohexane gives methyl 2-phenylethyl sulfoxide (XI, R=CH3) and dihydrobenzothiophene oxide (XII)(eq. 5). Photolysis of ethyl(2-o-iodophenyl)ethyl sulfone in... 

Moreover, N-sulfinyl oxazolidinones have been shown to be good intermediates for the synthesis of chiral sulfinate esters and sulfinamides with excellent ee. In all cases, the absolute configuration of the sulfoxide obtained is in agreement with the fact that nucleophilic displacement occurs with inversion of configuration at the sulfur center in the starting /V-sulfinyl oxazolidinone. 

Acyclic stereocontrol remains a challenging problem in synthesis. While enan-tiomerically pure sulfoxides are valuable synthetic intermediates for enantiocon-trolled carbon-carbon bond formation by conjugate addition in cyclic cases, their usefulness for such alkylations in acyclic cases has not been firmly established. Moreover, most sulfoxide directed alkylation protocols utilize the valuable sulfur auxiliary just once, which limits the synthetic versatility of the process. Marino et al. have recently reported SN2 displacements of acyclic allylic mesyloxy vinyl sulfoxides with organocopper reagents (Scheme 10).33 In addition to the excellent observed stereoselectivities, the newly created chiral center is adjacent to a vinyl sulfoxide which should allow for subsequent chirality transfer operations. On treatment with organocopper nucleophiles, both sulfoxide diastereoisomers 40b and 43b underwent SN2 displacements with high Z selectivity to yield products 42b and 45b, respectively (Table 2). The oxidation state on the sulfur was varied... 

In the presence of visible light irradiation provided by a 120 W lamp and with 1 atm of O2, the Ru(II) complex in solution promoted the oxidation of dibutyl sulfide to the corresponding dibutyl sulfoxide obtained in 32% yield. Under identical experimental conditions but in the presence of the capsule, the reaction did not occur as a consequence of the encapsulation of the Ru(ll) photocatalyst. The catalytic activity was restored when repeating the same experiment with [Ru(bpy)3] in the presence of both capsule and tetraethylam-monium competitive guest, due to the displacement of the metal catalyst from the cavity of the capsule. Similar results were observed with other thioethers showing conversions to the corresponding sulfoxides that were dependent on the electron density on the sulfur atom in all cases, no conversion was observed with the encapsulated Ru(ll) catalyst. Since it was danonstrated that the absorption properties of the Ru(ll) metal center were substantially not influenced by the capsule, it is likely that the inactivation provided by the capsule could be due to interrupted energy transfer from the Ru(ll) center to O2. 

The course of these radical displacements at the trivalent sulfur center of the sulfoxides is analogous to that observed for the sulfides the exocyclic displacement path obtains. Methyl (or t-butyl) o -ethylphenyl sulfoxide, the ultimate product of the alternative, endocyclic, displacement path is not observed. Our conclusion is also analogous the... 

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