Neopentyl tosylate

Alkyl sulfates, tosylates, and other esters of sulfuric and sulfonic acids can be converted to alkyl halides with any of the four halide ions. Neopentyl tosylate... 

Neopentyl sulfides have been prepared by alkylation of sodium sulfide with neopentyl tosylate in high-boiling polar solvents,4,5 or in low yields by reduction of alkyl 2,2-dimethylpropanethioate with the combination of lithium aluminum hydride and a large excess of boron trifluoride-etherate. ... 

Neopentyl tosylate p-Toluenesulfinic acid, neopentyl ester (8) Benzenesulfinic acid, 4-methyl-2,2-dimethylpropyl ester (9) (13146-08-2)... 

Neopentyl sulfides, 58, 146 Neopentyl tosylate, 58, 147 Nickle cathode, 57, 92 Nickle(U) chloride hexahydrate, 58, 128 Nickel, dichlorobis(triphenylphosphine), 58, 133... 

Sn2 reactions on neopentyl tosylates have been conveniently carried out in the solvents HMPA and Me SO Lewis Gustafson Erman Tetrahedron Lett. 1967, 401 Paquette Philips Tetrahedron Lett. 1967, 4645 Stephenson Solladi Mosher J. Am. Chem. Soc. 1972, 94, 4184 Anderson Stephenson Mosher J. Am. Chem. Soc. 1974, 96 3171. 

Alkyl sulfates, tosylates, and other esters of sulfuric and sulfonic acids can be converted to alkyl halides with any of the four halide ions.979 Neopentyl tosylate reacts with Cl, Br, or I without rearrangement in HMPA.980 Similarly, allylic tosylates can be converted to chlorides without allylic rearrangement by reaction with LiCl in the same solvent.981 Inorganic esters are intermediates in the conversion of alcohols to alkyl halides with SOCl2, PC15, PC13, etc. (0-67), but are seldom isolated. 

Different kinds of alkyl and aryl sulfonates 7 have been transformed to the fluorides 8 under fairly mild conditions with potassium fluoride in polyethylene glycol 400.145 No trace of elimination products, normally found due to attack of a second mole of potassium fluoride on the fluoroalkane eliminating hydrogen fluoride, is observed and the hydrolysis product is present only in 4% yield. No displacement of the tosylate group occurred for neopentyl tosylate. 

The initial work on the bicyclo[3.1.0]hexenyl system was reported by de Vries135 and Winstein and Battiste in I960136. It was shown that acetolysis of the tosylate 55 occurred with a 10 °-fold acceleration over neopentyl tosylate. The ionization of 55 was found to be anchimerically assisted with the predominant kinetic product of the reaction being the homofulvene 56. Small amounts of the acetate 57 were also present. Pentamethylbenzene, the anticipated product, was notably absent under kinetic control conditions. 

Reaction of the diol with p-toluenesulfonyl chloride in pyridine, however, produced the ditosylate in nearly quantitative yield. SN2 displacements by chloride on neopentyl tosylate, which bears certain structural similarities to the ditosylate precursor of CAMPHOS, have been shown to give good yields of neopentyl chloride. However, when l,2,2-trimethyl-l,3-bis(hydroxymethyl)-cyclopentane ditosylate was allowed to react with sodium chloride in hexa-methylphosphoramide, in an attempt to form the dichloride, only N, A -dimethyl-p-toluenesulfonamide was isolated. Reaction of the ditosylate with lithium chloride in ethoxyethanol was exothermic and HC1 was evolved but the dichloride was not isolated. The isolated product contained at least one oleflnic bond. Similarly, in N, TV-dimethylformamide, lithium chloride and the ditosylate gave a product that decomposed on distillation. Faced with such repeated failures, a dihalide route to CAMPHOS was abandoned in favor of a more direct approach reaction of the ditosylate with diphenylphosphide anion. 

Neopentyl tosylate reacts to form a cation under these conditions about 10 times as fast as ethyl... 

Neopentyl tosylate reacts with LiCl in HMPA and gives the chloride with clean inversion without rearrangement (equation 5). Another example of this reaction is the conversion of allylic tosylates to chlorides without rearrangement or reaction of the sensitive acetal (equation 6). Dimethylaminopy-ridine is a useful catalyst for the transformation of hydroxy compounds to chlorides with tosyl chloride. ... 

The above-mentioned reactions for the introduction of bromine always involve an activation of the alcohol as the first step. In some cases it can be useful to isolate the activated intermediate. The reactions of alkyl mesylates or tosylates with MgBr2 give alkyl bromides under mild conditions with good yields (equation 20) Neopentyl tosylate with LiBr in HMPA gives neopentyl bromide in 67% yield (equation 21). Complete inversion with little or no rearrangement is observed in this difficult case. 

A general method fen the synthesis of alkyl iodides is the reaction of tosylates or methanesulfonates with sodium iodide in acetone or magnesium iodide in diethyl ether (equation 30). The reaction is not always a clean Sn2 process. Stereoselectively deuterated neopentyl tosylate, for example, gives with Nal in HMPA only low yields (34%) of the racemic iodide (equation 31). This is in contrast to analogous reactions with bromide and chloride (see Sections 1.7.3.2 and 1.7.2.2), where better yields with complete inversion are observed. 

Anchimeric Assistance by Alkyl Groups The formolysis of neopentyl tosylate (612, X=OTs) is as rapid as that of ethyl tosylate whereas the rate of tri-fluoroacetoly sis is enhanced by a factor of 160. These data have been taken as evidence... 

Neopentyl tosylate reacts with lithium chloride in hexamethylphosphoric triamide (HMPA) and gives the chloride with clean inversion and without rearrangement21. The Mitsunobu procedure22-24 uses the strong oxophilicity of phosphorus for the activation. In this reaction, alcohols are converted to the corresponding halides with inversion of configuration by lithium salts24. 

Clearly, both spectra are of the tertiary 2-methylbutyl cation and the neopentyl cation never saw the light of day. The reaction is the same rearrangement that you saw in the substitution reaction of neopentyl iodide, but here the rate of rearrangement can be measured and it is extremely fast. Neopentyl tosylate reacts to form a cation under these conditions about 10 times as fast as ethyl tosylate, even though both tosylates are primary. This massive rate difference shows 1 that if migration of an alkyl group can allow rearrangement to a more stable carboca- nL qTs... 

As far back as 1960 Winstein and L. de Vries noted a high anchimeric acceleration (10 °) in the solvolysis of pentamethylcyclopentadienylcarbinol tosylate 484 as compared with neopentyl tosylate chosen as a model convenient for comparison. The kinetically controllable products in this reaction were olefine 485 and... 

Worthy of note is also the point of view of Traylor et al. on the mechanism of solvolysis of neopentyl-type systems. In their opinion the higher rate of reaction in the case of 2,2,3,3-tetramethylbutyl tosylate in comparison with neopentyl tosylate can be accounted for (at least partially) by the vertical stabilization of the developing carbonium centre by the electrons of the C —bond ... 

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