Methyl Fluorosulfate

Alkyl sulfonates are very effective cationic initiators of e-caprolactone, although only the more reactive methyl triflate and methyl fluorosulfate result in a high conversion. The mechanism of polymerization in the presence of these initiators is believed to involve methylation of the exocyclic carbonyl oxygen, followed by partial ring opening of the activated lactone by the counteranion (Fig. 

Methyl fluorosulfate has been used as a methylating agent in the formation of an S-methylthiepinium salt which was found to be more stable than the parent thiepin (149 equation 33) <77TL198S). 

In contrast to the original report1, it was established that on treatment with methyl fluorosulfate, compound 1 gives the non-crystalline fluorosulfonate, which is converted into the crystalline tetrafluoroborate 136 under the action of NaBF4161. An attempt to... 

Dimethyl(succinimido)sulfonium fluorosulfate 2, easily prepared from A -chlorosuccinimide (1), dimethyl sulfide, and methyl fluorosulfate, reacted with 1-dialkylaminocycloalkenes 3 to give fair yields of (2-dialkylaminocycloalk-l-enyl)dimethylsulfonium fluorosulfates 4 or their thermally rearranged allylic isomers At elevated temperatures 4 or 5, respectively, reacted... 

Cyclopropaniminium salts have been prepared in solution from cyclopropane-1,1-diamines by addition of methyl fluorosulfate, - bromine in liquid sulfur dioxide or dimethylchloronium tetrafluoroantimonate in liquid sulfur dioxide. Bicyclo[4.1.0]heptaniminium salts were obtained in fluorosulfonic acid at — 60 °C from a bicyclo[4.1.0]heptanone aminal or hemiaminal precursor or by the reaction of the corresponding aminal and methyl fluorosulfate in chloroform. A free cyclopropaniminium ion in solution also was assumed to be generated by the interaction of cyclopropanone hemiaminal with titanium(IV) chloride at — 78°C in di-chloromethane. ... 

Methyl fluorosulfate (0.147 g, 1.164mmol) was syringed at — 78°C into a solution of A,A-dimethylbi-cyclo[4.1.0]heptan-7-amine (0.106 g, 0.582 mmol) in CDClj (1 mL). Warming up to 20"C and filtration under N2 gave a yellow solution of the iminium ion. 

Dimethyl(succinimido)sulfonium fluorosulfate 2, easily prepared from /V-chlorosuccinimide (1), dimethyl sulfide, and methyl fluorosulfate, reacted with 1-dialkylaminocycloalkenes 3 to give fair yields of (2-dialkylaminocycloalk-l-enyl)dimethylsulfonium fluorosulfates 4 or their thermally rearranged allylic isomers 5.22 23 At elevated temperatures 4 or 5, respectively, reacted with nucleophiles Nu to give c -bicyclo[n.l.O]alkanes 8 or 9 via (Z,Z)-2-aminoallyl cation 6 or trans-bicyclo[n.l. 0]alkanes 12 via ( , Z)-2-aminoallyl cation 10, in fair to excellent yield.23 " 42 Normally, ra-annulated cyclopropylamines 8, resulting from kinetically preferred attack of... 

The reaction has been shown to be of very broad scope with a multitude of nucleophiles Nu such as imides.23,24,29,32,33,36,37,42 amines,10,32 cyanide,25,32 hydroxide,10,32 alkox-ide,10,26,32 electron-rich isocyclic or heterocyclic aromatic compounds,28 carboxamides,31 lactams,31 ureas,31 sulfonamides,31 cyanate,31 formate (to give products with Nu = H),34 C-H acidic compounds,35 hydrazines and hydrazides,38 and sulfinates.38 The amino group NR R2 of cyclopropane-1,1-diamines and the nucleophile Nu in bicycles 8, 9 or 12, respectively, can be easily replaced with other nucleophiles Nu, such as water,10,32,33 alkoxide,10,32-34,42 Grignard compounds,27,42 amines,29,30,36,37,42,43 cyanide,29,33,42,44 hydride,34,42,44 and C-H acidic compounds39-41,43,44 (see Section 5.2.1.). Therefore, it is currently the most important method for the preparation of substituted bicyclic cyclopropylamines. The toxic and costly reagent methyl fluorosulfate can be avoided in a modified synthetic route, which instead of the fluorosulfate 5 proceeds via the corresponding tetraphenylborate, hexafluorophosphate, or (most conveniently) via the tosylate.23 The different steps of the method can often be combined in a one-pot procedure. Results are summarized in Table 3. 

Methyl Fluoroacetate Methyl Fluorosulfate Methyl Hydrazine Methyl Iodide Methyl Isocyanate Methyl Mercaptan Methyl Vinyl Ketone Methyltrichlorosilane Nickel Carbonly (Nickel... 

Quaternization of 3,5-dimethyl- and 3,5-diphenyl-l,2,4-thiadiazole with methyl fluorosulfate produces, in the former case, the 4-methyl salt (375, Y = S03F, 60%), in the latter a mixture of the 4- and 2-methyl isomers (376,377 Y = S03F 9 and 34%). The quaternization sites were established both by chemical and X-ray techniques. The predominant 2-quaternization in 377 is ascribed to the electronic and steric effects of the two phenyl groups flanking N4 in 377.283... 

In a proposed preparation of tricyclic trisaminomethanes (45) (Table 6) tbe reaction of uncatalyzed exchange between etbyl ortboformate HC(OEt)3 and tbe macrocyclic triamine 1,4,7-triazacyclo-nonane (205) was initially unsuccessful. However tbe exchange reaction proceeded smoothly when the more reactive dimethylformamide dimethylacetal HC(OMe)2NMe2 was substituted for HC(OEt)3 to afford (45) in 88% yield <80JA6364> a stoichiometric amount of reactants either neat or in the presence of inert solvent at 120°C were used for performing the reaction. When (45) was treated with either Mel or methyl fluorosulfate, the dication (69) was formed. Compound (45) was reported to be prepared in 84% yield by the reaction of (205) with HC(OEt)3 in THE in the presence ofp-TsOH at 135°C for 60 h <80JA6365>. Most plausibly, such drastic conditions are needed because of the involvement of two unfavorable steps the formation of a strained formamidinium ion (95) as intermediate or the direct displacement of ethanol from the ester aminal intermediate (206) (Scheme 20). 

Methyl fluorosulfate, methyl 2,4,6-trinitrobenzosulfonate, and trimethyloxonium tetrafluoro-borate have been shown to serve as methylating reagents for the formation of S-methyl benzo-thiepinium salts (Equations (8)-(10)) <77TL1985, 83LA425,84ZN(B)985,90ZN(B)1573>. 

Formamide reacts with alkyl halides to furnish A -alkyl derivatives. Attack by the amidic oxygen on harder acceptors such as a-halo acids and esters has been revealed (106). Secondary amides undergo O-methylation with methyl fluorosulfate (107, 108). 

For example, methyl chloride or bromide reacts with F2S2O6 at —25 °C to give methyl fluorosulfate. The reaction is applicable to fluorochlorocarbons (eq 2). ... 

Hydrogen Abstraction. Reactions of (1) with a variety of organic compounds such as amines, alcohols, thiols, aromatics, and even saturated hydrocarbons, proceed by hydrogen abstraction and addition of an OSO2F moiety (R-H R0S02F). For example, methane gives a mixture of methyl fluorosulfate and methylene difluorosulfate. Methyl fluorosulfate also gives methylene difluorosulfate in reaction with (1) Hexafluoropro-pane and propionic acid react in accordance with eqs 4 and 5. 

Related Reagents. 2-Diazopropane l-Diazo-2-propene Dimethyl Sulfate Diphenyldiazomethane Methyl Fluorosulfate Phenyldiazomethane Trimethyloxonium Tetrafluoroborate Trimethyl Phosphate Trimethylsilyldiazomethane. 

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