Methanesulfonyl Chloride eliminations

Sulfonate Formation. The preparation of an alkyl methane-sulfonate from an alcohol can be achieved by treatment of an alcohol with methanesulfonic anhydride in the presence of pyridine or 2,4,6-collidine (eq 1). The use of methanesulfonic anhydride rather than methanesulfonyl chloride eliminates the formation of small amounts of alkyl chlorides which occurs when... 

In contrast to the behavior of homoallylic alcohol (70a) when treated with methanesulfonyl chloride is pyridine, heating A -19-methanesulfonate (68b) in pyridine gives the 5)5,19-cyclo-6-ene (72). Vinylcyclopropane (72) is inert to the conditions used for converting vinylcyclopropane (73) to the A ° -B-homo-7)5-ol (70a). The latter results are only consistent with the existence of two discrete isomeric carbonium ion intermediates which give rise to isomeric elimination products. °... 

On the basis of these findings, the reaction of acyl imines with methanesulfony 1 chloride-triethylamine is not expected to proceed via a sulfene intermediate as previously proposed [99]. Again, a carbanion intermediate accounts nicely for the experimental facts. The electrophihcity of the hetero-l,3-diene is exdemely high, therefore the carbanion, formed on reaction of triethylamme with methanesulfonyl chloride, should undergo nucleophilic attack at C-4 of the hetero-1,3-diene faster than sulfene formabon by chloride elimination. 

The application of lithiumtrimethylsilyl acetate for the C-l elongation of aldonolactones has been examined (73). Although the reagent had been successfully used for the alkenation of lactone carbonyl groups (74), in the case of aldonolactones 10b or 25b only insignificant yields of the alkenes, but 30 - 40% of the lactols 49a or 50a, were obtained (73). However, these lactols, alternatively prepared in good yields by a Reformatsky-type reaction (53,54), were readily eliminated to the desired alkenes by simple treatment with methanesulfonyl chloride-triethylamine at 0°. Thus, from 49a or 50a separable E,Z mixtures (76a and 76b, or 77a and 77b, respectively) were obtained in good yields (73). 

The reaction of Af,Af-dimethyl-( )-styrylamine (73) with a halogen-substituted methanesulfonyl chloride allowed the first stereoselective formation of the halogenated thietane 1,1-dioxide 74, which then could be converted to the corresponding thiete sulfone 75 via a Cope elimination of the corresponding AT-oxide. ... 

In certain cases in which the substrate carries an a hydrogen, there is strong evidence1728 that at least some of the reaction takes place by an elimination-addition mechanism (ElcB, similar to the one shown on p. 382), going through a sulfene intermediate,1729 e.g., the reaction between methanesulfonyl chloride and aniline. 

From a- or 0- substituted aldehydes or ketones by elimination reactions Benzeneselenenyl trichloride, 27 Methanesulfonyl chloride-4-Di-methylaminopyridine, 176 9-(Phenylseleno)-9-borabicyclo-[3.3.1]nonane, 245 By oxidation of allylic substrates Pyridinium chlorochromate-Benzo-triazole, 262 By other methods Alumina, 14... 

Methanesulfonyl chloride may be a new reagent to you. In the presence of a base (usually triethy-lamine, EtjN) it reacts with alcohols to give methanesulfonate esters, but the mechanism differs from the mechanism with TsCl. The first step is an elimination of HC1 from the sulfonyl chloride (this can t happen with TsCl, because there are no available protons) to give a sulfene. The sulfene is highly electrophilic at sulfur, and will react with any alcohol (including tertiary alcohols, which react very slowly with TsCl). Here are the two mechanisms compared, formation of toluenesuifonates (tosylates) reagents ROH + TsCl + pyridine... 

The use of optically active enamines in [2 + 2] cycloadditions with thiocarbonyl 5.5-dioxides gives asymmetric induction in the product thiirane 1,1-dioxides. Thus, when thioformaldehyde S,S-dioxide, generated from methanesulfonyl chloride and triethylamine, is treated with optically active AM-phenylethyl-Af-methylpropanal enamine, a mixture of diastereomeric thietane 1.1-dioxides 6 is formed quantitatively. Removal of the chiral 1-phenylethyl auxiliary followed by Hoffmann elimination gives (-+ )-(5)-2-methyl-2//-thiete 1,1-dioxide (7) with 6% ee1,8. 

The treatment of alcohols with methanesulfonyl chloride and triethylamine provides a rapid, convenient method for the preparation of mesylates, and these can be eliminated to furnish alkenes. 

Hydroxy selenides undergo elimination to alkenes when treated with an excess of methanesulfonyl chloride, but elimination is not an important side reaction in rearrangement reactions. ... 

The same elimination has been effected by Corey and Grieco with mesyl chloride (see Methanesulfonyl chloride, this volume). 

The preceding section dealt primarily with the evidence that demonstrated sulfenes to be intermediates in these processes and also, where the evidence warranted it, with the mechanism of the sulfene formation. A continual point of concern is whether or not the reaction is really proceeding by way of the sulfene or not. In this section we shall attempt to find what circumstances of substrate, base and (where different) nucleophile tend to lead to the elimination-addition (sulfene) reaction, and which to some other process, notably the direct displacement reaction. Sometimes, indeed, it takes only a rather small change in conditions to alter the mechanism completely. For example, it has been noted above that azide ion reacts with a-disulfones or sulfonyl chlorides by the direct displacement49. This is also seen in the reaction of methanesulfonyl chloride with aqueous sodium azide when the... 

Virtually all of the vast number of methanesulfonate, or mesylate , esters prepared to facilitate elimination or substitution of a hydroxyl function have been prepared from sulfene the standard procedure using methanesulfonyl chloride and triethylamine in dichloromethane has been described by Crossland and Servis138. To be sure, sulfene intermediacy is not required for alkanesulfonate ester formation the reaction, as has been noted (in Section IV.A.2), will proceed without base promotion via the direct displacement route, but it is usually sufficiently sluggish, however, that the further reaction of the ester with the alcohol competes with ester formation139. This makes the procedure a poor one for most practical purposes, although we recently encountered an instance, namely the preparation of neopentyl 2-chloroethanesulfonate87, in which the direct reaction of the alcohol and sulfonyl chloride without base was the method of choice this arose because (a) the product is stable and (b) 2-chloroethanesulfonyl chloride does not yield the corresponding sulfene with tertiary amines (Section IV.A.2). 

Linstead and coworkers" investigated alkali-catalyzed y3-elimination of the diacetate and dimethanesulfonate of dimethyl (+ )-3,4-dihydroxy-hexanedioate [(-I-)-/3,j8 -dihydroxyadipate] resulting in a trans,trans-muconic acid derivative. An unusually facile, double (irons )-jS-elimina-tion was found" in the reaction of dimethyl galactarate (15) with methanesulfonyl chloride in pyridine dimethyl irons,frans-2,5-di(methyl-sulfonyloxy)mucoate (17) was obtained by esterification to give 16... 

Alkenes can also be obtained by elimination of p-hydroxy selenides, under the action of methanesulfonyl chloride, thionyl chloride or other acidic conditions. The reaction is stereospecific, proceeding by anti elimination, by way of the epise-lenonium ion, e.g. 29 (2.28). High yields of di-, tri- or tetrasubstituted alkenes can be obtained and the reaction provides an alternative to the Wittig reaction when the phosphonium salt cannot be readily obtained. The p-hydroxy selenides can be prepared by a number of methods, for example from a-seleno aldehydes or ketones by reduction or reaction with a Grignard reagent, or from a-lithio selenides by... 

For primary and secondary alcohols, the hydroxyl is best made into a leaving group for elimination reactions by sulfonylation with para-toluenesulfonyl chloride (tosyl chloride, TsCl) or methanesulfonyl chloride (mesyl chloride, MeS02Cl or MsCl). 

Methanesulfonyl chloride by contrast has a feature it shares with the acyl chlorides just above a relatively acidic proton that can be removed by base. This deprotonation, followed by loss of chloride, is the first step in the formation of a mesylate ester. It is an ElcB elimination and the product is called a sulfene. 

These reagents are not effective for primary alcohols, as chlorides are formed instead. Alcohols can be dehydrated in a two-step sequence by conversion to a sulfonate ester (methanesulfonyl chloride or p-toluenesulfonyl chloride are used most frequently), followed by base-catalyzed E2 elimination. 

Analysis of Reagent Purity H NMR, IR, elemental analysis. Preparative Methods the title reagent is prepared by the reaction of 2-(methylsulfonyl)-3-phenyl-2-propenyl alcohol and phosgene (eq 1). The alcohol is obtained from the corresponding allylic bromide by formate-catalyzed hydrolysis. The synthesis of the bromide involves the Cu(OAc)2-catalyzed addition of methanesulfonyl chloride to -methylstyrene followed by elimination of hydrogen chloride and subsequent free radical bromination of the methyl group (eq 1). ... 

Elimination of water from a /-alcohol in a p-hydroxy aldehyde was carried out using an excess of Methanesulfonyl Chloride-DMAP-H20 at 25 C. ... 

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