Sulfonate esters rearrangement

Efremov and coworkers observed that electron-donating groups promote the sulfoxide-sulfonate ester rearrangement in the molecular ions of 2,4-dinitrophenyl... 

Ester eliminations are normally one of two types, base catalyzed or pyrolytic. The usual choice for base catalyzed j5-elimination is a sulfonate ester, generally the tosylate or mesylate. The traditional conditions for elimination are treatment with refluxing collidine or other pyridine base, and rearrangement may occur. Alternative conditions include treatment with variously prepared aluminas, amide-metal halide-carbonate combinations, and recently, the use of DMSO either alone or in the presence of potassium -butoxide. 

Sulfonate esters and halides can also migrate in this reaction. a-Halo and a-acyloxy epoxides undergo ready rearrangement to a-halo and a-acyloxy ketones,... 

The other fragmentation pathways are typical for diaryl sulfoxides "" . A corresponding ortho effect was found in chlorodiphenyl ethers and sulfides but not in sulfones (12) were the sulfinate ester rearrangements " and the consequent formation of the m/z 125 and m/z 159 ions suppress the other possible fragmentations of the molecular ions (equation 4). It is also noteworthy that the ratio [m/z 125] [m/z 159] increases with increasing distance between the chlorine and the sulfur (equation 4). 

Pedersen and coworkers investigated the El mass spectra of several 2-hydroxyphenyl alkyl sulfones (39) and sulfoxides (Section II.B). The methyl derivative seemed to fragment only via sulfinate ester formation giving the primary product ions m/z 157 and 109 (equation 14). Obviously hydrogen bonding between the ortho hydroxyl and the sulfone sulfur makes the loss of CH3SO2 difficult in contrast to the situation in methyl phenyl sulfone. The sulfinate ester rearrangement is not important when R>Et in 39. 

Phenanthro[4,5-fc,c,d]thiophene-4,4-dioxide (20) fragments mainly via the cyclic sulfinate ester (Section II.D). Naphthothiete sulfone (65) rearranges also to a cyclic sulfinate (66) prior to fragmentation, as shown by the similarities in their El mass spectra . The parent SO ion at m/z 308 which was much less pronounced for 65 than for 66 (10 vs. 54%) indicated, however, that the former does not decompose exclusively via 66. 

Trifluoromethanesulfonates of alkyl and allylic alcohols can be prepared by reaction with trifluoromethanesulfonic anhydride in halogenated solvents in the presence of pyridine.3 Since 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 appropriate precautions must be taken to ensure structural and stereochemical integrity. Tertiary alkyl sulfonates are neither as easily prepared nor as stable as those from primary and secondary alcohols. Under the standard preparative conditions, tertiary alcohols are likely to be converted to the corresponding alkene. 

Scheme 49) [148], Recently, it has been demonstrated that phenolic sulfonate esters used as photoacid generators cleave into radical fragments the resulting phenoxyl radical has been detected by transient optical absorption [149], Similar photochemical rearrangements have been reported in pyrymidinic systems [150], An example is shown in Scheme 50 [151]. 

This route requires a hydrogen a to the carbonyl function and may give rearrangement in the dehydration step (Sections 8-9B and 15-5E). Alternatively, the hydroxyl can be converted to a better leaving group (halogen or sulfonate ester), which then may be displaced by H e (as LiAlH4 see Table 16-6) ... 

Sulfonic Esters by Rearrangement of Alkyl Sulfites (RO)jSO RSOjR (56%) ... 

Activation of the oxime with benzenesulfonyl chloride or p-toluenesulfonyl chloride leads to sulfonate esters which undergo the Beckmann reaction with or without isolation. - The sulfonate esters also rearrange under mild reaction conditions on silica gel.i Under neutral conditions, lV,A(-carbonyldiimida-zole activates oximes in the presence of allyl bromide, followed by spontaneous Beckmann rearrangement. ... 

Neber rearrangement. Formation of a-amino ketones by treatment of sulfonic esters of ketoximes with potassium ethoxide, followed by hydrolysis. 

An ambident anion is one with different kinds of atoms which may become attached to a carbocation. Isomerization of the anionic portion permits detection of ion pair return in close analogy to the equilibration of 180 labeled benzoate or sulfonate esters. The isomerization of thiocyanates (112) to isothiocyanates (113) is the most studied of these ambident rearrangements 5, "6 In some respects these reactions differ from the return processes of carboxylate or sulfonate ion pairs ... 

Olefins react with SO3 under free-radical conditions to afford cyclic sulfonate esters, i.e., sultones.The initially formed products are believed to be the highly strained 1,2-adducts, which then rearrange to the 1,3-adducts. This is the commercial route to propanesultone. 

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