Alkyl tosylates

As alkylating agent an alkyl halide, alkyl tosylate or dialkyl sulfate is used in most cases the latter type of reagent is often used in the preparation of methyl and ethyl ethers by employing dimethyl sulfate and diethyl sulfate respectively. Dimethyl sulfate is an excellent methylating agent, but is acutely toxic as well as carcinogenic." ... 

Alcohols react with p-toluenesulfonyl chloride (tosyJ chloride, p-TosCl) in pyridine solution to yield alkyl tosylates, ROTos (Section 11.1). Only the 0-H bond of the alcohol is broken in this reaction the C—O bond remains intact, so no change of configuration occurs if the oxygen is attached to a chirality center. The resultant alkyl tosylates behave much like alkyl halides, undergoing both SN1 and Sjsj2 substitution reactions. 

Steady-state approximation. The following scheme is suggested for the hydrolysis of sec-/ -aryl-alkyl tosylates ... 

Table 10B Relative rates of reaction of some alkyl tosylates with ethanol at 25 °C...

The selective N-monoalkylation of anilines with alkyl halides and alkyl tosylates under microwave irradiation has been described by Romera and coworkers (Scheme... 

Consistent with this mechanism is the fact that the reaction takes place with inversion of configuration at the reaction centre (Johnson and Nidy, 1975). For alkyl tosylates similar results have been reported (San Fillippo et al., 1975). The formation of alcohols under these conditions has been ascribed to secondary reactions (Chern et al., 1978 Johnson et al., 1978). Under certain conditions alcohols are even the only isolated products (Corey et al., 1975). 

Alkyl tosylates and mesylates are cleaved on the action of KOj in DMSO and give rise to the corresponding alcohols. This reaction also proceeds with inversion of configuration at carbon atoms (Morkovnik and Okhlobystin 1979). Such process may be of importance in prostaglandin chemistry. 

Although there are many claims in patents to the preparation of alkylguanidines by reaction of guanidine with alkyl halides, this method, which was first studied by Schenck [ 16 5 ], has only rarely been found satisfactory. Primary and secondary alcohols in 80-85 per cent sulphuric acid react with guanidines to give the mono-and di-alkyl derivatives [166]. A process for direct alkylation of guanidine by an alkyl tosylate has been developed [95, 138, 167]. 

Trifluoromethanesulfonates of alkyl and allylic alcohols can be prepared by reaction with trifluoromethanesulfonic anhydride in halogenated solvents in the presence of pyridine.3 Because the preparation of sulfonate esters does not disturb the C—O bond, problems of rearrangement or racemization do not arise in the ester formation step. However, sensitive sulfonate esters, such as allylic systems, may be subject to reversible ionization reactions, so that appropriate precautions must be taken to ensure structural and stereochemical integrity. Tertiary alkyl tosylates are not as easily prepared nor as stable as those from primary and secondary alcohols. Under the standard conditions, tertiary alcohols are likely to be converted to the corresponding alkene. 

Alkylation (with dialkyl sulfates, alkyl tosylates, and alkyl halides) and arylation (with nitro-activated aryl halides) of the llf-naphtho[l,8-deltriazine (89) and of the structurally related 6,7-dihydro-lif-... 

Symmetrical ethers are obtained from the dehydration of two molecules of alcohol with H2SO4 (see Section 5.5.3). Alcohols react with p-toluenesul-phonyl chloride (tosyl chloride, TsCl), also commonly known as sulphonyl chloride, in pyridine or EtsN to yield alkyl tosylates (see Section 5.5.3). Carboxylic acids, aldehydes and ketones are prepared by the oxidation of 1° and 2° alcohols (see Sections 5.7.9 and 5.7.10). Tertiary alcohols cannot undergo oxidation, because they have no hydrogen atoms attached to the oxygen bearing carbon atom. 

Conversion of alcohols by sulphonyl chlorides preparation of alkyl tosylates or tosylate esters... 

Alcohols react with sulphonyl chlorides to yield sulphonate esters via Sn2 reaetions. Tosylate esters (alkyl tosylates) are formed from alcohols from the reaetion with p-toluenesulphonyl ehloride (TsCl). The reaction is most commonly carried out in the presenee of a base, e.g. pyridine or triethyla-mine (Et3N). 

Similarly, alkyl tosylate reacts with other nucleophiles, e.g. H, X , HO , R 0 , R , NH2 or NH3, CN, Ns" and R C02 following the Sn2 reaction mechanism, and produces a number of other functional groups as follows. 

The use of alkyl tosylates generally leads to predominant TV-alkylation (e.g. 76JOC875), as does the alkylation of the thallium salts of pyrrole or indole (70JCS(C)2563,71JOC3993,81S389). 

Alcohol p-Toluenesulfonyl chloride Alkyl p-toluenesulfonate (alkyl tosylate)... 

NaOH, (PhCH2NEt3)Cl allylic bromide, benzylic bromide, 1° alkyl tosylate SL 171 (1994)... 

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