2- Phenylsulfonyl-l,3-dienes

Aziridinocyclopropanes 163 derived from 2-phenylsulfonyl-l,3-dienes undergo BF3-induced rearrangement to bicyclic amines 165, which feature the skeleton of the tropane alkaloids. The reaction proceeds via cyclopropyl carbinyl cation 164, an intermediate also invoked in the analogous epoxide rearrangements. Trapping by fluoride ion is a competing pathway <96TL3371>. 

Phenylsulfonyl-l,3-dienes.1 This reagent undergoes selective 1,2-addition to 1,3-dienes, particularly at low temperatures. Oxidation of the adducts provides 2-phenylsulfonyl-1,3-dienes. 

Selenosulfonylation of olefins in the presence of boron trifluoride etherate produces chiefly or exclusively M products arising from a stereospecific anti addition, from which vinyl sulfones can be obtained by stereospecific oxidation-elimination with m-chloroper-benzoic acid134. When the reaction is carried out on conjugated dienes, with the exception of isoprene, M 1,2-addition products are generally formed selectively from which, through the above-reported oxidation-elimination procedure, 2-(phenylsulfonyl)-l,3-dienes may be prepared (equation 123)135. Interestingly, the selenosulfonylation of butadiene gives quantitatively the 1,4-adduct at room temperature, but selectively 1,2-adducts at 0°C. Furthermore, while the addition to cyclic 1,3-dienes, such as cyclohexadiene and cycloheptadiene, is completely anti stereospecific, the addition to 2,4-hexadienes is nonstereospecific and affords mixtures of erythro and threo isomers. For both (E,E)- and ( ,Z)-2,4-hexadienes, the threo isomer prevails if the reaction is carried out at room temperature. 

This procedure illustrates a highly selective and facile method for introducing a phenylsulfonyl group into the Z-position of 1,3-diene systems by using commercially available starting materials. The method can be applied to cyclic as well as acyclic systems giving 2-(pheny1sulfonyl)-l,3-dienes. In an alternative synthesis via condensation of allyl sulfone with aldehyde and subsequent acylation-elimination, the 2-(phenylsulfonyl)-l,3-dienes obtained are limited to acyclic systems. 

Allylic and dienyl sulfones have been prepared by conjugate addition to 1,3-dienes ". Phenylsulfonyhnercuration of conjugated dienes gives mercury adducts which can be treated with base to afford phenylsulfonyldienes. 2-(Phenylsulfonyl)-l,3-dienes can be stereo- and regioselectively functionalized via Michael addition of nucleophiles to give allylic sulfones. A key intermediate in the synthesis of a Monarch butterfly pheromone 4 was prepared by BackvaU and Juntunen by alkylation and subsequent palladium-catalyzed substitution of the allylic sulfone formed by Michael addition of dimethyl malonate to 2-(phenylsulfonyl)-l,3-butadiene (equation 10). 

The electron-deficient double bond in 2-phenylsulfonyl-l,3-dienes underwent regioselective cyclopropanation with sulfur ylides in very good yield, e.g. cyclopropanation of 13, 14 and 15 with sulfur ylides.140 On the other hand, the use of zinc-copper couple and diiodomethane afforded a 83 17 mixture of vinylcyclopropanes 16 and 17 from 2-(phenylsulfonyl)cyclohexa-1,3-diene (15) in moderate yield. The reaction at the electron-deficient double bond rather than at the expected electron-rich double bond shows that the Simmons-Smith carbenoid is fairly nucleophilic in character.140... 

Electron-deficient 1,3-dienes are potentially interesting Diels-Alder dienes. In our study with different kinds of olefins, we observed that 2-(phenylsulfonyl)-l,3-dienes show a duality 1n their Diels-Alder cycloaddition reactions, giving [4+2] adducts with both electron-deficient and electron-rich olefins.3 This dual reactivity of the 2-(phenylsulfonyl)-l,3-dienes in [4+2] cycloaddition increases the role they can play in organic synthesis. 

The preparations of the starting sulfones are also given [404]. See [405] for the synthesis of 2-(phenylsulfonyl)-l,3-cyclohexadiene and related dienes. 

Cheng et al. [316] synthesized the polymer-bound 2-sulfony-l, 3-dienes from the corresponding support-bound suhblene, which upon thermal S02-extrusion gave the highly reactive diene (345), which could be trapped with dienophiles. The synthesis on a polystyrene support begins with polymer-bound lithium phenyl-sulfinate. S-Alkylation with trans-3, 4-dibromosulfolane (343) in the presence of pyridine gave the resin-bound 3-(phenylsulfonyl)-3-sulfolene. Thermal SO2 extrusion had to be performed in xylene under reflux, which restricts the use of this reaction to PS/DVB-resins. Neither the IRORY-Kans [317] nor the Synphase Crowns [199], which are made of polypropylene, are compatible with these reaction conditions, in which polypropylene is dissolved (Scheme 72) ... 

A reoxidation of the catalytic amounts of hydroquinone (HQ) to benzoquinone (BQ) in Scheme 8-11 by molecular dioxygen was realized by the use of an oxygen-activating macrocyclic metal complex as cocatalyst [53,62-65]. This leads to a mild biomimetic aerobic oxidation which is now based on a triple catalytic system (Scheme 8-12). With this system cyclohexa-1,3-diene is oxidized to frans-l,4-diacetoxycyclohex-2-ene at room temperature in 85-89% (>91% tmns) [62]. With the use of 2-phenylsulfonyl-l,4-benzoquinone as quinone, the trans selectivity of this process was >97% [53]. 

The heterocyclic double bond in simple indoles will take part in cycloaddition reactions with dipolar 4n components,and with electron-deficient dienes (i.e. inverse electron demand), in most reported cases, held close nsing a tetherf° a comparable effect is seen in the intermolecular cycloaddition of 2,3-cycloalkyl-indoles to ortfto-quinone generating a l,4-dioxane. ° The introduction of electron-withdrawing substituents enhances the tendency for cycloaddition to electron-rich dienes 3-acetyl-1-phenylsulfonylin-dole, for example, undergoes aluminium-chloride-catalysed cycloaddition with isoprene, " and 3-nitro-l-phenylsulfonylindole reacts with l-acylamino-buta-l,3-dienes without the need for a catalyst. Both 3- and 2-nitro-l-phenylsulfonyl-indoles undergo dipolar cycloadditions with azomethine ylides. ... 

Reports on the synthesis of diene complexes using Fe2(CO)9 are more common. Reaction of 2-phenylsulfonyl-1,3-cyclohexadiene with 2equiv. of Fe2(GO)9 in refluxing ether formed the [l-(phenylsulfonyl)-l,3-cyclohexa-diene]iron(0)tricarbonyl isomer 26. The reaction is catalyzed by 1-aza-1,3-butadiene. In a separate study, 1-aza-1,3-butadienes were shown to effect a quantitative catalytic complexation of cyclohexadienes with Fe2(GO)9. Activities are greatly enhanced in the presence of aryl rings bonded to nitrogen. 

Dimethyl(phenyl)silyllithium can be added as a nucleophile to the tricarbonyl(ri -cyclohexa-l,3-diene)iron complex. Quenching the reactive intermediate with trifluoro acetic acid provides l-dimethyl(phenyl)silylcyclohex-l-ene, whereas treatment with 2-(phenylsulfonyl)-3-phenyloxaziridine affords predominantly the corresponding [r) -2-dimethyl(phenyl)silylcyclohexa-l,3-diene]iron complex as the major product... 

The ring expansions of cydohexadiene derivatives to azepines is of historical significance, as the first example of a monocyclic 1//-azepine was obtained by cyanide ion attack on 2-acetoxy-2,4,6-trimethyl-iV-(phenylsulfonyl)cyclohexa-3,5-dien-l-imine (4) 17 however, it was almost twenty years before the product was correctly formulated as the l//-azepine 5.24... 

Methyl-5-phenylsulfonyl-3(2iJ)-pyridazinone (152, R = SOaPh) underwent Diels-Alder addition by 2,3-dimethyl-l,3-butadiene (151) to give 2,6,7-trimethyl-4a-phenylsulfonyl-4a,5,8,8a-tetrahydro-1 (2fl)-phthalazinone (153, R = S02Ph) (reactants, PhH, reflux, 10 days 90%) methyl l-methyl-6-oxo-l,6-dihydro-4-pyridazinecarboxylate (152, R = C02Me) likewise gave methyl 2,6,7-trimethyl-1 -oxo-1,2,4a,5,8,8a-hexahydro-4a-phthalazinecarbox-ylate (153, R = C02Me) (70%) such additions by an unsymmetric diene... 

Oxazolidin 5-Methylen-4-phenylsulfonyl-2,3,3-trimethyl-E15/1, 363 (1,2-Dien + Nitron) l-Thia-5-aza-spiro[5.5]undec-2-en ... 

It is well established that 3-alkyl pyridines are selectively reduced at N1-C2, to produce 3-alkyl-l,2-DHPs [58,59,60], 5-Alkyl-l,2-DHPs, which result from hydride addition at C-6, are potentially valuable synthetic intermediates [61]. Substituent effects on the regiochemistry of the reduction of A-carbalkoxypyridinium salts have been studied in detail by Sundberg [62]. These DHPs have served as useful dienes for the synthesis of ISQs. Methyl 2-[l-phenylsulfonyl-lH-indol-2-yl]-2-propenoate (62) served as dienophile in most of these reactions [61,62,63,64,65,66,67,68]. Palladium-catalyzed radical cyclization [63], photocyclization [64] or thermal cyclization [61,65,66,67,68] reactions have all been employed to furnish the Diels-Alder adducts (e.g., 63). 

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