Acyl sulfonates

The aromatic sulfonyl chlorides which have no a-hydrogen and thus cannot form sulfenes give acylic sulfones. Thus 1-piperidinopropene on reaction with benzene sulfonyl chloride (9J) gave 2-benzenesulfonyl-l-piperidinopropene (153). Similarly the enamine (28) reacts with p-toluene-sulfonyl chloride to give the 2-p-toluenesulfonylcyclohexanone (154) on hydrolysis (/OS). 

As discussed in Section 4.10.6.1, due to low electron density at the carbon atoms, electrophilic reactions such as acylation, sulfonation, and nitration do not occur readily. In the presence of an amino group at C(2), the 5-bromo derivative can be prepared <84CHEC-I(4)545>. 

The dicyclopentadienyl metal compounds undergo Friedel-Crafts alkylation and acylation, sulfonation, metalation, arylation, and formyla-tion in the case of ferrocene, dicyclopentadienyl ruthenium, and dicyclopentadienyl osmium, whereas the others are unstable to such reactions ( ). Competition experiments (128) gave the order of electrophilic reactivity as ferrocene > ruthenocene > osmocene and the reverse for nucleophilic substitution of the first two by n-butyl lithium. A similar rate sequence applies to the acid-catalysed cleavage of the cyclopentadienyl silicon bonds in trimethylsilylferrocene and related compounds (129), a process known to occur by electrophilic substitution for aryl-silicon bonds (130). 

Reaction of the a-nitrosulfones (2) with aqueous TiCl3 results unexpectedly in nitriles, RC=N, in about 75% yield, a-Nitrosulfones are oxidized in alkaline solution by excess KMn04 to carboxylic acids, RCOOH, in 80-90% yield, probably via the acyl sulfone. 

There is a very large number of complexes which contain one or two Cp groups per iron atom the best known is the unusually stable ferrocene for which a vast organic chemistry is known.117 It undergoes Friedel-Crafts acylation, sulfonation, and metallation by alkyllithiums, and so on. An example is the reaction... 

Beau, J M, Sinay, P, D-Glycopyranosyl phenyl sulfones acylation of their lithiated anions and reductive desulfonylation of the resulting acylated sulfones. A synthesis of a-D-C-glycosides, Tetrahedron Lett., 26, 6193-6196, 1985. 

Alkylation, acylation, sulfonation and silylation occur on the N-atoms of imidazoles [116]. Other reagents substitute onto the C-atoms 4 and 5, which are equivalent as a result of annular tautomerism. 

Systems with a pyrrole-like N-atom can be alkylated, acylated, sulfonated and silylated. Subsequent conversion into quaternary compounds is possible. 

Hydrolysis of the enaminone (23) in acidic aqueous medium gave, in good yield, 58-hydroxymethylene pristinamycin (26). This compound was readily acylated, sulfonated and phosphorylated, using standard conditions, affording the corresponding 0-acyl, 0-sulfonyl and 0-phosphonyl derivatives (27). 

Isotope effects are also useful in providing insight into other aspects of the mechanisms of individual electrophilic aromatic substitution processes. In particular, since primary isotope effects are expected only when the breakdown of the rate-determining, the observation of a substantial kn/ko points to rate-determining deprotonation. Some typical isotope effects are summarized in Table 9.7. While isotope effects are rarely observed for nitration and halogenation, Friedel-Crafts acylation, sulfonation, nitrosation, and diazo coupling provide examples in which the rate of proton abstraction can control the rate of substitution. 

N-[o>-(Carbalkoxyamino)acyl]sulfonic acid amides 43,295 o-(Carbalkoxyamino)benzylsilanes... 

Sulfonates s. Acyl sulfonates. Metal —, Phosphonium —, Sulfonic acid esters Suifonation s. a. Replacement of hydrogen by sulfonic acid groups N-Sulfonation 17, 355 Sulfones Cs. a. Replacement of sulfonyl groups, C- and a-Sulfonyl. . . )... 

Oxidative Cleavage. Once the desired stereochemistry is obtained, the phenyl sulfone serves its final purpose during oxidative cleavage using ozone. The immediate product formed is presumably an acyl sulfone which can be converted to an ester (eq 6) or an amide (eq 7). In the absence of an external nucleophile, an internal alcohol can be used to form a lactone (eq 8). ... 

Acylation at a is facile (on Q, or -dianions) and requires an extra equivalent of base for the acidic a-acyl sulfone products. Aldehydes and ketones react similarly at a to afford -hydroxy sulfones. Spontaneous cyclization occurred (eq 3) when the al-lylic alcohol from acrolein was oxidized to the unsaturated ketone (eq 3) and treatment with base completed the conversion to 3-methylcyclopentenone. However, mesylation of the -hydroxy sulfone gave the four- instead of six-membered cyclization in eq 3 by direct rather than aUyUc displacement. Other cyclizations are shown in eq 4, the epoxide yielding only the six-membered ring, the dibromo derivative both five- and six-membered rings. 

Acylsolfides s. Thiolic acid esters Acyl sulfonates... 

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