Sulfur dioxide insertion reaction

Dichlorocarbene is a typical singlet ground-state carbene which is commonly used for cydopropanation reactions, since it gives satisfactory yields in many cases, but in general, carbene synthesis implies a metal catalyst (usually copper) together with a diazo compound as the carbene precursor. In (he particular case of the O -H insertion reaction, sulfur dioxide has been reported as being an efficient catalyst for the insertion of carbalkoxycarbenes generated from diazoesters. 

A direct insertion of sulfur dioxide into a C—C bond has been observed under photochemical conditions 3 (equation 72) a related CH insertion followed by an intramolecular sulfinate to carbonyl addition yields the same system 3 (equation 73). A further sulfolene synthesis utilizes a three-component reaction see equation 74 (cf. Section IV below) 35. 

Reactions like these, where they have been tested, have also proved to be suprafacial on the conjugated system. Thus the reversible insertions of sulfur dioxide into the stereochemically labelled butadienes 2.178 and 2.179 take place stereospecifically, and suprafacially. 

The insertion of sulfur dioxide with Fe(f -C5H5)R(CO)2 is highly stereospecific, as shown by reaction (c), in which an enantiomeric complex yields the corresponding optically active S-sulfinato derivative. 

The migration (insertion) reaction may also occur in the case of many other unsaturated molecules such as SO2, CO2, N2, NO, nitriles, isonitriles, and ketones. The insertion of sulfur dioxide may proceed very rapidly. The NMR and IR measurements show that the reaction proceeds through O-sulfinates which subsequently undergo rearrangement to give stable S-sulfinates ... 

Also, insertion of sulfur dioxide into the Co-C bond of organocobaltoximes is observed The insertion of sulfur dioxide into a C-H bond in alkenes leads to their isomerization via a retro-reaction sequence . 

Tnfluoromethanesulfinate can be prepared from the reaction of trifluoromethyl bromide with sulfur dioxide and zinc [50] (equation 41) Similar insertion occurs when perfluoroalkyl iodides are used as precursors (equations 41 and 42)... 

Codeposition of silver vapor with perfluoroalkyl iodides at -196 °C provides an alternative route to nonsolvated primary perfluoroalkylsilvers [272] Phosphine complexes of trifluaromethylsilver are formed from the reaction of trimethyl-phosphme, silver acetate, and bis(trifluoromethyl)cadmium glyme [755] The per-fluoroalkylsilver compounds react with halogens [270], carbon dioxide [274], allyl halides [270, 274], mineral acids and water [275], and nitrosyl chloride [276] to give the expected products Oxidation with dioxygen gives ketones [270] or acyl halides [270] Sulfur reacts via insertion of sulfur into the carbon-silver bond [270] (equation 188)... 

Palladium(II) complexes possessing bidentate ligands are known to efficiently catalyze the copolymerization of olefins with carbon monoxide to form polyketones.594-596 Sulfur dioxide is an attractive monomer for catalytic copolymerizations with olefins since S02, like CO, is known to undergo facile insertion reactions into a variety of transition metal-alkyl bonds. Indeed, Drent has patented alternating copolymerization of ethylene with S02 using various palladium(II) complexes.597 In 1998, Sen and coworkers also reported that [(dppp)PdMe(NCMe)]BF4 was an effective catalyst for the copolymerization of S02 with ethylene, propylene, and cyclopentene.598 There is a report of the insertion reactions of S02 into PdII-methyl bonds and the attempted spectroscopic detection of the copolymerization of ethylene and S02.599... 

The S02 molecule has unshared pairs of electrons on both the sulfur and oxygen atoms. As a result, it forms numerous complexes with transitions metals in which it is known to attach in several ways. These include bonding through the sulfur atom, through an oxygen atom, by both oxygen atoms, and various bridging schemes. In most cases, the complexes involve soft metals in low oxidation states. Another important reaction of sulfur dioxide is known as the insertion reaction, in which it is placed... 

Insertion Reactions of Transition Metal-Carbon o--Bonded Compounds II. Sulfur Dioxide and Other Molecules, 12, 31... 

Sulfur dioxide will insert into Pt—carbon bonds (Section 52.4.8.4). Evidence has also been presented that sulfur dioxide will coordinate to the axial ends of the bimetallic Ptn-Pt11 complex Pt2(P205H2)4- the reaction is an equilibrium process and no structural data are given.1495... 

Xlld does not involve the chiral center, so if the reaction takes place by this pathway, the migration of the alkyl group from sulfur to palladium (with the concomitant or subsequent loss of sulfur dioxide) must take place with inversion of configuration at carbon. Inversion of configuration at carbon has been observed in the reverse-type reaction, the sulfur dioxide insertion into a carbon-iron sigma bond (49). Nucleophilic displacement at carbon in compounds of type Xld is unusually difficult, so the reaction via the sulfite intermediate Xlld would appear to be more likely. Conversion of the tosylate of l-phenyl-2,2,2-trifluoroethanol to the corresponding chloride, a reaction which takes place in the presence of tetra- (n-butyl) ajnmonium chloride with inversion of configuration at carbon, requires 100°C for 24 hrs in dimethylsulfoxide. 

Organogold(I) complexes undergo a number of insertion reactions with unsaturated molecules, such as olefins, acetylenes, and sulfur dioxide. Insertion of carbon monoxide or carbon dioxide has not been achieved, although the reverse reaction has been observed with C02 (7/). 

Sulfur dioxide is capable of reacting with metal alkyl, aryl or u-allyl complexes in an insertion-type reaction to yield S-sulfinate (4), O-sulfinate (5) or 0,< -sulfinate complexes (6).13 It can also insert into the metal-metal bond in the cobalt complex (7) to give the S02-bridged complex (8).38... 

Another anomalous cycloaddition is the insertion of a carbene into an alkene. 6-Electron cheletropic reactions (p. 28) are straightforward allowed pericyclic reactions, which we can now classify with the drawings 3.47 for the suprafacial addition of sulfur dioxide to the diene 2.179 and its reverse. Similarly, we can draw 3.48 for the antarafacial addition of sulfur dioxide to the triene 2.180 and its reverse. The new feature here is that one of the orbitals is a lone pair, which is given the letter co to distinguish it from o- and n-bonds, with suprafacial and antarafacial defined by the drawings 3.45 and 3.46, which apply to all sp3 hybrids and p orbitals, filled or unfilled. 

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