Insertion reactions with sulfur compounds

Arnaudet, Folcher, and Marquet-Ellis [32] have reported that, as monitored by NMR, CP3UR compounds also undergo insertion reactions with sulfur dioxide (eq.(20)). Unfortunately, the products are only stable... 

In the reaction with sulfur compounds such as thiophenes, S-C insertion proceeds as shown in eq. (18.27) [47-49]. 

The thiazyl cation is used for the preparation of other important S-N compounds. For example, the insertion reactions with S4N4 or SC12 produce [S5N5]"1" or the acyclic [C1SNSC1]+ cation,62 respectively, and the reaction with sulfur gives [S2N]+ salts. 

Insertion reactions with carbon monoxide or sulfur dioxide are well known for compounds with carbon-transition-metal bonds, e.g.,... 

Sulfur dioxide also forms complexes with a number of metal species and may be bound in different ways. In the crystalline compound SbF5-S02, which is of interest because of the use of S02 as a solvent for super acid systems (page 174), the S02 is bound as in (15-VI).54 Sulfur dioxide also forms numerous complexes with transition metals, as well as undergoing insertion reactions with M—M and M—C bonds which are discussed... 

Insertion reaction with silyl azides. Sulfur trioxide (as the 1 1 complex with dioxane) undergoes insertion with silyl azides and with compounds having a tri-... 

One of the other reactions with organozinc compounds are insertion reactions to sulfur dioxide or oxygen. For example, dialkylzinc reacts with sulfur dioxide to give almost quantitatively an insertion product to the zinc-carbon bond as shown in eq. (5.37) [94],... 

Rhodium(II) carbenoid intermediates are also useful. For example, carbene transfer reaction with allylic sulfides followed by [2,3]-sigmatropic rearrangement of the resulting sulfur ylides (Doyle-Kirmse reaction) gives furan-containing sulfides 133 in good yields (Scheme 19.32) [50]. In contrast, reaction with allylic compounds (R—H) or alcohols/amines/thiols/silanes (X—H) furnishes the 1,1-insertion products 134 or 135, respectively [51],... 

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. 

The reaction of tetrachlorodisilane with chalcogenation reagents is one of the synthetic methods to bis-nor-adamantane or double-decker type compounds. When a solution of di-terf-butyltetrachlorodisilane 66 in THF is refluxed together with one equivalent of lithium sulfide or stirred with lithium selenide at room temperature, the tetra(ferf-butylsilicon)pentachalcogenides 67 and 68, respectively, are formed (Scheme 18)6. Each pentachalcogenide exhibits one resonance of a ferf-butyl group in the H and 13C NMR spectra. Most likely, the bis-nor-adamantane derivatives 69 and 70 are initially formed. Insertion of a sulfur or selenium atom into one of the two strained Si—Si bonds would then lead to the observed products. 

This is the second chapter of a two-part review concerned with insertion reactions of transition metal-carbon a-bonded compounds. The first chapter, which appeared in Volume 11 of this series (137), provided a broad introduction to the subject of insertion reactions in general and a detailed treatment of the carbon monoxide insertion and decarbonylation. Presented herein are the insertion and elimination reactions of sulfur dioxide and of a few other unsaturated molecules. The reactions of sulfur dioxide are accorded a complete literature coverage, whereas those of the other inserting species are treated selectively. Metal-carbon a-bonded compounds of the main group elements are discussed only in the context of comparisons with their transition metal analogs. 

Although SO2 insertion is a clean reaction for many metal-carbon complexes, some metal alkyls, e.g., PhCH2Cr(H20)s (4), decompose rapidly to unidentified materials upon treatment with sulfur dioxide. At the other end of the reactivity scale, a number of metal-carbon a-bonded compounds are inert to SO2. These include, in particular, perfluoro-alkyls and -aryls such as CF3Mn(CO)s (66) and CpFe(CO)2CeF5 (13), as well as other complexes with electron-withdrawing substituents in the o-bonded carbon fragment (71). 

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. 

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