Sulfonyl group

Active methylene or methine compounds, to which two EWGs such as carbonyl, alko.xycarbonyl, formyl, cyano, nitro, and sulfonyl groups are attached, react with butadiene smoothly and their acidic hydrogens are displaced with the 2,7-octadienyl group to give mono- and disubstituted compounds[59]. 3-Substituted 1,7-octadienes are obtained as minor products. The reaction is earned out with a /3-keto ester, /9-diketone, malonate, Q-formyl ketones, a-cyano and Q-nitro esters, cya noacetamide, and phenylsulfonylacetate. Di(octadienyl)malonate (61) obtained by this reaction is converted into an... 

An advantage that sulfonate esters have over alkyl halides is that their prepara tion from alcohols does not involve any of the bonds to carbon The alcohol oxygen becomes the oxygen that connects the alkyl group to the sulfonyl group Thus the configuration of a sulfonate ester is exactly the same as that of the alcohol from which It was prepared If we wish to study the stereochemistry of nucleophilic substitution m an optically active substrate for example we know that a tosylate ester will have the same configuration and the same optical purity as the alcohol from which it was prepared... 

The reaction of alcohols with acyl chlorides is analogous to their reaction with p toluenesulfonyl chloride described earlier (Section 8 14 and Table 15 2) In those reactions a p toluene sulfonate ester was formed by displacement of chloride from the sulfonyl group by the oxygen of the alcohol Carboxylic esters arise by displacement of chlonde from a carbonyl group by the alcohol oxygen... 

Polar groups, eg, carbonyl and sulfonyl, that are capable of conjugation with the aromatic ring increase the glass-transition temperature, eg, to 245°C for the sulfonyl group, as in (5). 

The amino and sulfonyl groups on the benzene ring should be in the 1,4 positions the amino group should be unsubstituted or converted to a free amino in vivo. 

Pyrazolines substituted at position 4 or 5 with hydroxy or amino groups readily eliminate a molecule of water or amine yielding pyrazoles. The 4-substituted derivatives are relatively more stable than the 5-substituted ones, because for the last group the lone pair at N-1 assists the elimination (407) -> (408) -> (409). The sulfonyl group at position 1 is also easily eliminated and this property is taken advantage of in Dorn s elegant synthesis of 3-aminopyrazole (Section 4.04.3.3.1). 

The reaction exhibits other characteristics typical of an electrophilic aromatic substitution. Examples of electrophiles that can effect substitution for silicon include protons and the halogens, as well as acyl, nitro, and sulfonyl groups. The feet that these reactions occur very rapidly has made them attractive for situations where substitution must be done under very mild conditions. ... 

The dienophilic character of imines parallels that of carbonyl compounds Consequently, electron deficient imtnes are the most reactive dienophiles of this class, particularly those having C perfluoroalkyl [5, 146, 150, 228], /V-acyl [/2i5 127], or A/-sulfonyl groups [148, 229 230]... 

Mesomerism involving sulfonyl groups is relatively weak, and in the case of the sulfonyliminopyridones (279) destabilization caused by the factors previously mentioned for the acyliminopyridones should be less important. Early ultraviolet spectral comparisons showed that acetylsulfapyridine and sulfapyridine (cf. reference 354) exist in aqueous solution as mixtures of comparable amounts of 279 and 280. A recent investigation of 2-, 3-, and 4-methanesulfonamido-... 

Some other examples of sulfonyl group nucleophilic displacements utilized in drug design are illustrated in Scheme 186 (95EUP683159,97FA405,97JMC463). 

In a similar treatment of 3,4-bis(alkylsulfonyl)furoxans, both sulfonyl groups were eliminated (Scheme 191) (86H889). Bis(isoxazoline) 294 was isolated in 10-17% yield. 

Products 2a-c, after removal of the sulfonyl groups, are suitable for the preparation of other 1,5-diazocine derivatives (see Section 1.5.1.3.). 

In contrast cyclic y-(rey/-butyldimethylsilyloxy)-a,/ -unsaturated sulfones undergo addition of organometallic reagents to give mainly trans-adducts after reductive removal of the sulfonyl group. 

Reactivity ratios for the copolymerization of AN with 7 in methanol at 60 °C, proved to be equal to rx AN= 3,6 0,2 and r%n = 0 0,06, i.e., AN is a much more active component in this binary system. The low reactivity of the vinyl double bond in 7 is explained by the specific effect of the sulfonyl group on its polarity26. In addition to that, the radical formed from 7 does not seem to be stabilized by the sulfonyl group and readily takes part in the chain transfer reaction and chain termination. As a result of this, the rate of copolymerization reaction and the molecular mass of the copolymers decrease with increasing content of 7 in the initial mixture. 

Dediazoniations which give aryl-addition or aryl-substitution derivatives of compounds with double bonds are discussed in this and the following section. Reactions at the C or S atom of carbonyl or sulfonyl groups are treated in this section and those at C = C double bonds in Section 10.9. 

Rearrangements of this type are unifold transformations, which show [l.n]shifts of the sulfonyl group within the carbon moiety. 

In allyl sulfones 1,3-migrations of the sulfonyl group take place thermally49 51 or Pd(0)-catalyzed52 (equation 11). 

Reaction products of concomitant anionotropic 1,3-shifts to nitrogen and 1,5-shifts to carbon of sulfonyl groups in azo coupling products ofa-methoxy /J-oxo sulfones have been found under thermal conditions55,56 (equation 14). 

Sulfonanilides suffer 1,3- and 1,5-shifts of the sulfonyl group under various conditions. The reactions may be spontaneous58-60, thermal61,62, photochemical62,63, base-catalyzed61,64,65, acid-catalyzed66-69 or oxidative70 (equation 15). 

In principle, sulfonyl compounds bearing highly-electron-accepting substituents are able to transfer the sulfonyl group as an electrophile. Thus, the exchange of aryl substituents in methyl aryl sulfones under catalysis of trifluoromethanesulfonic acid takes place258 (equation 46). This reaction represents a further example for the reversibility of Friedel-Crafts reactions. 

Sulfonic acids themselves are unfit for electrophilic transfer of sulfonyl groups because of the poor nucleofugality of the hydroxide anion. However, the high acidity obviously leads to an equilibrium between the acids and their anhydrides and water, from which water can be removed either by special reaction conditions (i.e., azeotropic distillation with appropriate solvents) or chemically with anhydride forming agents316 (equation 63). sulfonic acid anhydride sulfonylations are compiled in Table 10. 

---