Tosyl 521915 225056722 2008-07-11T17:57:41Z 137.122.187.43 [[Image:Tosyl.png|thumb|right|175px|The [[tosyl|tosylate]] group with [[R|a generic 'O-R' group]] attached]] [[Image:Tosylate-3D-balls.png|thumb|right|175px|[[Ball-and-stick model]] of the tosylate anion]] A '''tosyl''' group (abbreviated '''Ts''' or '''Tos''') combines the [[toluene]] and [[sulfonyl]] [[functional groups]]. The sulfonyl group consists of a [[hexavalent]] sulfur [[atom]] [[double bond]]ed to two [[oxygen]] atoms and, in the tosylate group, an [[aromatic ring]]; an [[alkyl]] [[substituent]] on the R group forms a [[sulfonate]] [[ester]]. Thus, the tosylate group is the ester of [[toluenesulfonic acid]]. The [[arene substitution patterns|para orientation]] illustrated (p-toluenesulfonyl) is most common, and by convention ''tosyl'' refers to the p-toluenesulfonate ester. A tosylate ester has only a limited shelf life if it is stored outside of a [[desiccator]] as the free tosyl is readily [[hydrolysis|hydrolysed]] by water in the presence of light. The tosyl group is [[electron withdrawing group|electron-withdrawing]]. Hence, it is an excellent [[leaving group]]. The tosyl group is also a [[protecting group]] for [[alcohol]]s, prepared by combining the alcohol with [[sulfonyl chloride|toluenesulfonyl chloride]] in an [[aprotic solvent]]. Toluenesulfonyl chlorides activate alcohols for [[nucleophile|nucleophilic attack]] or [[elimination]] ([[dehydration]]). Similarly, the '''brosyl''' ('''Bs''') group or brosylate is a p-bromobenzenesulfonyl group with the methyl group of toluene replaced by a [[bromine]] atom. '''Nosyl''' groups in Nosylates ('''Ns''') are 4-nitrobenzenesulfonyl groups with a [[nitro]] group in the [[para isomer|para]] position. The CAS registration number is 98-59-9. == Applications == The use of these functional groups is examplified in [[organic synthesis]] of the drug [[tolterodine]], where in one of the steps a [[phenol]] group is blocked as a tosyl group and the primary [[alcohol]] as a nosyl group. The latter is a leaving group for displacement by [[diisopropylamine]] <ref>{{cite journal | title = Reduction of Ethyl Benzoylacetate and Selective Protection of 2-(3-Hydroxy-1-phenylpropyl)-4-methylphenol: A New and Facile Synthesis of Tolterodine | author = Kathlia A. De Castro, Jungnam Ko, Daejong Park, Sungdae Park, and Hakjune Rhee | journal = [[Organic Process Research & Development]] | year = 2007 | doi = 10.1021/op7001134 | format = ASAP article | volume = 11 | pages = 918}}</ref><ref>Reaction sequence: [[organic reduction]] of ''ethyl benzoylacetate'' by [[sodium borohydride]] to a diol, followed by [[Friedel-Crafts alkylation]] with [[p-cresol]] and [[iron(III) chloride]] to a phenol. The tosyl and nosyl groupds are introduced as their respective chlorides with either [[sodium hydroxide]] or [[triethylamine]] as a base. The next step is [[nucleophilic displacement]] of the nosyl group by [[diisopropylamine]], The remaining tosyl group is removed by another round of NaOH. Not shown: [[optical resolution]] by [[tartaric acid|L-tartaric acid]] to optically pure (R)-isomer</ref>: :[[Image:TolterodineSynthesis.png|400px|Tolterodine synthesis]] ==References== {{Reflist}} [[Category:Functional groups]] [[Category:Leaving group]] [[es:Tosilo]] [[fr:Tosylate]] [[ko:토실기]] [[pl:Tosyl]] [[pt:Tosil]]