Sulfones, allenic

A chirality transfer from the allenic sulfone 154 to the Diels-Alder adducts is observed in the reaction of (+)-(S)-l-(p-tolylsulfonyl)buta-l,2-diene with cyclopentadiene (equation 112), in which the diastereomers 155 and 156 are formed predominantly107. 

Scheme 4.58 Chiral allenic sulfones from asymmetric selenoxide elimination.

The reaction of 1,2-allenylphenylsulfone with dibenzylamine afforded (E)-2 (dibenzylamino)-l-propenylphenyl sulfone 212 [112], Based on this reaction, racemic allenic sulfones can be partially resolved with optically active amines [113],... 

Cycloadducts with great synthetic potentialities have been easily obtained from the reactions of dienes with allenic sulfones (ArS02CH=C=CH2) and acetylenic sulfones (essentially ArSO,C=CH, but some disubstituted acetylenes (R S02C=C-R2) have been used). A few applications are briefly summarized in the following schemes. 

TABLE 3.8. Silver-Catalyzed Preparation of Allenic Sulfones... 

In a related reaction, Harmata and Huang showed that allenic sulfones were easily prepared from propargylic sulhnates (Table 3.8). Catalyst screening showed that silver nitrate was ineffective, whereas silver tetrafluoroborate and hexafluoroanti-monate worked well in dichloromethane, chloroform, or nitromethane at room temperature. All reactions were very rapid, within 2 min, and were very effective in terms of yield.78... 

Claisen rearrangement. The Claisen rearrangement of highly substituted allyl vinyl ethers can proceed readily even when two vicinal quaternary centers are formed. Thus addition of an allylic Icohol (1) to an allenic sulfone (2) provides the allyl vinyl ether... 

A large amount of woik has been accomplished using mixed sulfiir/selenium reagents, such as seleno-sulfides and selenosulfones. One example of selenosulfide addition via radicals is selenotbiolactoniza-tion. When selenosulfide (15) is treated with AIBN, a mixture of y-seleno-substituted thiolactones is produced (equation 9). Although these lactonizations result in mixtures of stereoisomers, they usually can be separated. In addition to these reports, selenosulfones have been used to form allenic sulfones, alkynic sulfones and (phenylsulfonyl)(Uenes (S< me4). ... 

The effects of aryl groups were kinetically analyzed by comparing the rate constants of both steps (ki for oxidation step and /C2 for elimination step) which were determined by NMR analysis of the concentration of vinyl selenides, the intermediate selenoxide, and allenic sulfones [16b]. This kinetic study indicates that the rates of both oxidation and elimination steps were accelerated by the introduction of an electron-withdrawing group. Such acceleration has been known in the overall selenoxide elimination as well as in the selenoxide elimination step of alkyl aryl selenides. As a result, it was disclosed that the ratio of these rate constants (/C1//C2) was closely related to the enantiomeric excess of the products the smaller the ratio, the larger the enantiomeric excess becomes. Thus, the introduction of o-nitrophenyl group as an aryl moiety, which suppresses sterically the racemization of the intermediate chiral selenoxide and accelerates the selenoxide elimination step, is necessary to achieve a higher asymmetric induction. 

In an extensive study Etenmark could elaborate conditions to control the formation of the conjugated or the (in most cases thermodynamically more stable) deconjugated system.With terminal monofunc-tionalized allenic sulfones one observes predominantly attack from the sterically less hindered face of the allene leading to trans adducts (equation 41). 

The adducts of the reaction of allyl alcohols with allenic sulfones are especially interesting as they allow the carbanion-accelerated Claisen rearrangement to take place. By deprotonation, or directly by addition of an allyl alcoholate anion, a system is generated, which rearranges much more easily than the uncharged system and with high diastereoselectivity (Scheme 62). 

Aryl vinyl selenides (86) are oxidized by (—)-(69) to selenoxide intermediates which undergo elimination to chiral allenic sulfones (87) (Scheme 17) <93JOC3697>. Other homochiral oxaziridines such as (74) gave lower ees. In a related study asymmetric oxidation of cyclohexyl selenides (88) with ( —)-(69) gives axially chiral cyclohexylidine derivatives (89) in up to 83% ee (Equation (18)) <93JA5847>. 

A carbanion -accelerated hetero-Cope rearrangement was reported by Blechert 170). Reaction of the sodium salt of the hydroxamic acid (202) with the allene sulfone 203 led at 0 °C within 10 min to 206. Undoubtedly, the carbanions 204 and 205 are the important intermediates in this transformation. A carbanion -accelerated... 

Acetylenic and allenic sulfones in syntheses of heterocycles by 1,3-dipolar cycloaddition 01T5263. 

Formation of fused heterocycles from acetylenic or allenic sulfones and pyrroles or furans as dienes 01T5263. 

The oxidation of the propargyl sulfide (469) with MCPBA and sodium carbonate as base was accompanied by a prototropic rearrangement to the corresponding allene sulfone (470) the same product was formed by oxidation of the parent allene sulfide (471). 

The hydroboration described in reaction A of Fig. 5 mainly occurs on the (R)-alkene and leaves the unreacted (,S)-oIefin having a 65% e.e. [29]. A similar level of stereoselection (70% e.e.) was estimated for the unreacted (R)-allenic sulfone recovered from the conjugate addition of half equivalent of (R)-a-methylbenzylamine to the racemic compound (reaction B) [30]. 

Scheme 7-36 Mechanistic rationale for the design of DNA-cleaving molecules of the propargylic and allenic sulfone type (Nicolaou et al.)-...

Allenes, 57, 285, 286, 356 Allcnic aldehydes, 189-190 Allenic amides, 169 AUenic boranes, 285, 286 Allenic esters, 301 Allenic ethers, 320 Allenic ketones, 189-190, 301 Allenic sulfones, 395 Allylacetophenone, 7-8 AUylbenzene, 292 Allyl bromide, 133, 292 Allyl diazoacetate, 222 Allyl esters, 302 Allyl ethers, 136-137 Allylic acetates, 176, 534 Allylic alcohols, 6, 136, 141, 142, 179, 191, 260, 335, 346, 373, 379-380, 427, 428, 445, 451-452,534 r-AUylic alcohols, 426-427 Allylic amination, 43 Allylic amines, 176 Allylic carbamates, 316 Allylic chlorides, 516 Allylic esters, 173, 243 Allylic ethers, 534 Allylic halides, 334-335 Allylic hydroperoxides, 247, 316, 317, 370... 

Resolution of allenic sulfanes. The allenic sulfone buta-l,2-dienyl /i-tolyl sulfone, CHgC6H4S02CH=C=CHCH3, can be resolved to the extent of 70% by treatment with 0.5 equiv. of (R)-a-phenylethylamine, ao +40°, in ether at 25°. The recovered sulfone is optically active. ... 

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