Sulfur reaction with diazoalkanes

The use of excess diazoalkane in its reaction with sulfur dioxide will necessarily lead to symmetrically substituted thiirane dioxides. When monoalkyl or monoaryl diazoalkanes are used, mixtures of cis- and trans-isomers are formed18-19-99. 

Vinyl sulfoxides have been used as synthetic equivalents of alkynes in reactions with diazoalkanes to prepare pyrazoles. The initially obtained adducts subsequently eliminate or rearrange the sulfoxide moiety to achieve pyrazoles lacking the sulfur function. Thus, the adducts resulting by reaction of CH2N2 with the sulfinylated double bond of allenyl sulfoxides 213 are transformed through a sulfoxide-sulfenate rearrangement into hydroxymethyl pyrazoles 214 [168], whereas those obtained by reaction with sulfinyl coumarins 215 suffered sulfinyl elimination into the pyrazoles 216 [169]. In both cases l,H-pyrazoles were obtained as a consequence of a final tautomerization step (Scheme 101). These studies were carried out on racemic sulfoxides. 

Monoalkyl- and monoaryldiazoalkanes yield, on treatment with sulfur dioxide, cis/lrans mixtures of episulfones. However, in the reaction of disubstituted diazoalkanes with sulfur dioxide mainly trans-isomers are formed112-115,... 

In addition to the unsubstituted sulfene itself, the various substituted sulfenes used in the preparation of thietane 1,1-dioxides are listed in Table 4. Although the usual method for generating the sulfenes is by treatment of a methanesulfonyl chloride with triethylamine, sulfenes have been obtained by the reaction of phenyl-methanesulfonyl fluoride with phenyllithium, by treatment of a-chloro-ethanesulfinic acid with refluxing triethylamine,by treatment of 4-nitro-phenyl or 2-chloro-4-nitrophenyl, esters of arylmethanesulfonic acids with potassium t-butoxide or 2,6-dimethylpyridine, respectively, by treatment of diazoalkanes with sulfur dioxide" (e.g., to give 146) and by thermolysis of a Diels-Alder adduct of sulfene." ... 

The high nucleophilicity of a-selenoalkyllithiums towards carbonyl conqiounds, even those that are the most hindered or enolizable, such as 2,2,6-trimethyl- and 2,2,6,6-tetramethyl-cyclohexanone (Schemes 113 and 164), di-t-butyl ketone, pennethylcyclobutanone, peimethylcyclopenta-none (Schemes 113 and 187) °- and deoxybenzoin (Schemes 115, 116 and i65y 4 49 23 iqws the synthesis of related alkenes, epoxides and rearranged ketones which are not available from the same carbonyl compounds on reaction with phosphorus or sulfur ylides - or diazoalkanes. ... 

Another synthetic route to episulfides is by reaction of a diazoalkane (18) with either sulfur or a thioketone (19) (Scheme 13). 

The three-, four-and five-membered cyclic sulfones have some interesting reactions. Three-membered ring sulfones, called thiirane-1,1-dioxides or episulfones, can be prepared by reaction of a diazoalkane, e.g. (160), with sulfur dioxide (Scheme 63). The reaction affords a mixture of the cis-episulfone (161) and trans-episulfone (162), and both isomers can be isolated by fractional crystallisation at low temperature. Another method of preparation of episulfones is by treatment of a diazoalkane with a sulfonyl chloride (containing a-hydrogen atoms) and a tertiary amine (Scheme 64). Both these syntheses involve the formation of the highly reactive sulfene intermediate (163) (see Chapter 7, p. 114) episulfones on warming eliminate sulfur dioxide to form the alkene (164) as indicated in Scheme 64.7... 

---