Allylic sulfonylation reactions

Similarly, enamino vinyl sulfones (345) can undergo a thermally allowed electrocyclic reaction between the termini of the enaminic double bond and the allyl sulfonyl portion in the intermediate anion (346) to afford a, /1-unsaturated thiene dioxides (348) as shown in equation 126335. 

Other nucleophiles have been used in this reaction. For example, BINAP was shown to be the best ligand for the enantioselective allylic amination of 19 with sodium diformylamide, a protected ammonia equivalent, furnishing the desired product in good yield and excellent enantioselectivity [96]. Also, a P,N-ligand has been developed for the allylic sulfonylation with good ee but moderate yield [97]. 

After conversion to unsaturated sulfonates through reaction with vinyl or allyl sulfonyl chlorides, both primary and secondary alkenols afford dihydro-1,2-oxathiane 2,2-dioxides through a Ru-catalysed RCM (Scheme 55) <06T9017>. 

Chuard et al. used allylsulfoxides as precursors of oxygen-centered radicals (Scheme 83) [229]. The Evans-Mislow rearrangement of allylsulfoxides leads to allyl sulfonyl ethers. The authors decided to use those as source of oxygen radicals. In addition, when the allyl sulfoxide was branched on a cyclobutene, the tandem reaction delivered a cyclobutyloxy radical that collapsed and underwent ring expansion in good overall yield. Thus, starting from sulfoxide 283,... 

Li and coworkers have reported BiuNI-catalyzed allylic sulfonylation of a-methyl styrene derivatives with sulfonyl hydrazides 143 using TBHP (Bu OOH) as the terminal oxidant (Scheme 4.73) [115]. The mechanism of this reaction involves the generation of sulfonyl radicals, Ts, from sulfonyl hydrazides 143 by the BU4NI/TBHP catalytic system, followed by the addition of Ts to a-methyl styrene derivatives 142 to give the corresponding allylic sulfones 144. 

As the previous shown amination reaction, Lyubimov et al. [54b,58] investigated the palladium-catalyzed allylic alkylation with dimethyl malonate and allylic sulfonylation of ( )-l,3-diphenylallyl... 

Allylic sulfonylation with sodiumpara-toluenesulfinate was investigated with ligands 46 and 47, where the catalytically active species was prepared in situ (Table 22.23). The same effect as in the previous allylic substitution reaction was observed. The electron-withdrawing ligand 47 led to a decrease in conversion and enantiomeric excess, whereas with the electron-donating ligand 46 full conversion and an ee of up to 92% were observed. 

By analogy with the catalytic allylic alkylation performed with C-nucleo-philes described in Section 7.2.2.3, Plietker et al. used benzyl mercaptan as an S-nucleophile toward an isobutyl carbonate in the presence of an NHC-Fe complex 9. Allylic thioethers were obtained in 82% yield as a mixture of two regioisomers [eqn (7.7)]. The same group also investigated the sulfonylation of allylic carbonates with a-sulfonyl succinimides as S-nucleop-hiles. In this case, a base-free catalytic system generated in situ by thermal release of the SIMes carbene from its chloroform adduct in the presence of [Bu4N][Fe(CO)3(NO)] was adopted. Addition of DBU to the reaction mixtures allowed the one-pot synthesis of vinyl sulfones through a tandem iron-catalysed allylic sulfonylation/amine-catalysed isomerisation process. Remarkably, base-induced decomposition of the iron catalyst was not observed. 

Removal of the carbonate ring from 7 (Scheme 1) and further functional group manipulations lead to allylic alcohol 8 which can be dissected, as shown, via a retro-Shapiro reaction to give vinyl-lithium 9 and aldehyde 10 as precursors. Vinyllithium 9 can be derived from sulfonyl hydrazone 11, which in turn can be traced back to unsaturated compounds 13 and 14 via a retro-Diels-Alder reaction. In keeping with the Diels-Alder theme, the cyclohexene aldehyde 10 can be traced to compounds 16 and 17 via sequential retrosynthetic manipulations which defined compounds 12 and 15 as possible key intermediates. In both Diels-Alder reactions, the regiochemical outcome is important, and special considerations had to be taken into account for the desired outcome to. prevail. These and other regio- and stereochemical issues will be discussed in more detail in the following section. 

Bordwell and Cooper211 drew attention to the inertness of a-halosulfones and related compounds towards nucleophilic displacements of the halogen. Thus chloromethyl p-tolyl sulfone reacts with potassium iodide in acetone at less than one-fiftieth of the rate for n-butyl chloride. On the other hand, l-(p-toluenesulfonyl)-3-chloro-l-propene reacts about 14 times faster than allyl chloride. This contrast (and other comparisons) led the authors to attribute the inertness of a-halosulfones to steric hindrance, which was eliminated when the sulfonyl group was more remote from the reaction center. 

Pathway A shows the most common reaction where the nucleophilic substitution reaction occurs at the electron-deficient carbon atom due to the strong electron-attracting character of the sulfonyl group. Nucleophilic displacements at the allylic position (SN2 reaction) are shown in pathway B. Pathway C is the formation of a-sulfonyl carbanion by nucleophilic attack on the carbon atom p to the sulfone moiety. There are relatively few reports on substitution reactions where nucleophiles attack the sulfone functionality and displace a carbanion as illustrated in pathway D3. 

Ueno and coworkers10 have found that the facile displacement of sulfonyl group from a-alkylated allyl p-tolyl sulfones 18 by tri-n-butyltin radical in the presence of 2,2 -azobis[2-methylpropanenitrile] (AIBN) occurs smoothly in refluxing benzene (equation 11). In contrast, vinyl sulfones undergo the radical substitution reaction to give vinylstannanes in the presence of AIBN at a higher temperature11. 

The chiral a-pyrrolidino imine that is formed in situ in the reaction of a-sulfonyl amide 141 with allylic zinc reagents undergoes addition with mod-... 

Nucleophilic addition to a, -unsaturated sulfones has long been known. For example, treatment of divinyl sulfone with sodium hydroxide has been known to afford bis( -hydroxyethyl) sulfone "", while the reaction of a- and -naphthyl allyl sulfones and allyl benzyl sulfone " with alkali hydroxide or alkoxide gave -hydroxy or alkoxy derivatives. In the latter reaction, the allyl group underwent prototropy to the 1-propenyl group, which in a subsequent step underwent nucleophilic attack . Amines, alcohols and sulfides are known to add readily to a, -unsaturated sulfones, and these addition reactions have been studied widely. In this section, the addition of carbon nucleophiles to a, ji-unsaturated sulfones and the reactions of the resulting a-sulfonyl carbanions will be examined. 

Nucleophilic Substitution of xi-Allyl Palladium Complexes. TT-Allyl palladium species are subject to a number of useful reactions that result in allylation of nucleophiles.114 The reaction can be applied to carbon-carbon bond formation using relatively stable carbanions, such as those derived from malonate esters and (3-sulfonyl esters.115 The TT-allyl complexes are usually generated in situ by reaction of an allylic acetate with a catalytic amount of fefrafcz s-(triphenylphosphine)palladium... 

The allylation reaction has also been used to form rings. (i-Sulfonyl esters have proven particularly useful in this application for formation of both medium and large rings.122 In some cases medium-sized rings are formed in preference to six- and... 

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