Sulfone-based olefination reaction

Kocienski, P. Recent sulfone-based olefination reactions. Phosphorus Sulfur 9S5, 24,477-507. 

There are several new methodologies based on the Julia olefination reaction. For example, 2-(benzo[t/Jthiazol-2-ylsulfonyl)-j -methoxy-i -methylacetamide 178, prepared in two steps from 2-chloro-iV-methoxy-jV-methylacetamide, reacts with a variety of aldehydes in the presence of sodium hydride to furnish the ajl-unsaturated Weinreb amides 179 <06EJOC2851>. An efficient synthesis of fluorinated olefins 182 features the Julia olefination of aldehydes or ketones with a-fluoro l,3-benzothiazol-2-yl sulfones 181, readily available from l,3-benzothiazol-2-yl sulfones 180 via electrophilic fluorination <06OL1553>. A similar strategy has been applied to the synthesis of a-fluoro acrylates 185 <06OL4457>. 

In a pivotal modification of the direct olefination reaction Kocienski and his coworkers [10] showed that the use of l-phenyl-lff-tetrazol-5-yl sulfones, preferentially with NaHMDS or KHMDS as the base and DME as the solvent, provides olefins in excellent yields and stereoselectivity with respect to -isomers. The modified version of the direct olefination reaction has frequently been referred to as the Julia-Kocienski olefination reaction. 

The olefination reaction of BTFP sulfones could be performed with aldehydes and ketones. Efficiency and stereoselectivity of the process was influenced by various factors, such as structural features, base, solvent, etc. General trends are summarized in Table 20. 

The reaction between a carbanion derived from alkyl 3,5-bis(trifluoromethyl)phenyl sulfones and aldehydes affords, with good yields and stereoselectivities, the corresponding 1,2-disubstituted alkene through the Julia-Kocienski olefination reaction. This one-pot protocol can be performed using the phosphazene base at —78 °C and has been successfully used in a high yielding and stereoselective synthesis of various stilbenes such as resveratrol [47] (Scheme 5.28). 

Generation of Sulfur Ylides Julia Olefination and Related Processes. Recently, the modified Julia olefination, which employed certain heteroarylsulfones instead of the traditional phenyl-sulfones, has emerged as a powerful tool for alkene synthesis. Although the reaction was first reported with LDA, bases such as LHMDS, NaHMDS, and KHMDS are now commonly used. In addition, solvent as well as base counter-cation have been shown to markedly affect the stereochemical outcome of the olefination reaction. For instance, KHMDS was less selective than NaHMDS for the coupling between benzothiazoylsulfone (1) and cyclopropane carboxaldehyde (2) in toluene, furnishing a 3.7 1 ratio compared to a 10 1 ratio favoring the Z-isomer. However, both bases provided a 1 1 mixture of isomers when the reaction was run in DMF (eq 54). ... 

Tributyltin-1,3-dienes have been synthesized from tributyltin substituted benzothiazolyl sulfones and aldehydes via a Julia olefination reaction. The selectivity of the process proved higher in the presence of KHMDS as base (Scheme 96) [190]. 

Primary nitroparaffins react with two moles of formaldehyde and two moles of amines to yield 2-nitro-l,3-propanediamines. With excess formaldehyde, Mannich bases from primary nitroparaffins and primary amines can react further to give nitro-substituted cycHc derivatives, such as tetrahydro-l,3-oxa2iaes or hexahydropyrimidines (38,39). Pyrolysis of salts of Mannich bases, particularly of the boron trifluoride complex (40), yields nitro olefins by loss of the amine moiety. Closely related to the Mannich reaction is the formation of sodium 2-nitrobutane-1-sulfonate [76794-27-9] by warming 1-nitropropane with formaldehyde and sodium sulfite (41). 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

Amide-Based Sulfonic Acids. The most important amide-based sulfonic acids are the alkenylarnidoalkanesulfoiiic acids. These materials have been extensively described ia the Hterature. A variety of examples are given ia Table 5. Acrylarnidoalkanesulfoiiic acids are typically prepared usiag technology originally disclosed by Lubrizol Corporation ia 1970 (80). The chemistry iavolves an initial reaction of an olefin, which contains at least one aHyhc proton, with an acyl hydrogen sulfate source, to produce a sulfonated intermediate. This intermediate subsequendy reacts with water, acrylonitrile, and sulfuric acid. 

Block and Aslam441 reported a novel variant of the Ramberg-Backlund reaction in which a,/J-unsaturated a -bromoalkyl sulfones 368 afforded 1,3-dienes upon treatment with base. Since a -bromoalkyl sulfones 368 can be obtained readily by the initial treatment of olefins with bromomethanesulfonyl bromide under photoirradiation and subsequent treatment with triethylamine, this reaction was utilized for preparation of dienes which contain one additional carbon over that of the corresponding olefin. Starting from the cyclic olefins 369-372 the 1,3-dienes 373-376 were obtained442. 

Like the nitrone-olefin [3 + 2]-cycloaddition, the nitrone-allene [3 + 21-cycloaddition also takes place regioselectively to furnish methylene-substituted isoxazoli-dine derivatives. The substituents of the 3- and 4-positions of the cycloadducts 72a and 72b are disposed cis in contrast, the reaction of 70 with allenyl sulfone 71c gives rise to the trans-cycloadduct 72c exclusively (Table 12.4). On treatment with base or heating, methyleneisoxazolidines 72 readily rearrange to isoxazo-lines via a 1,3-hydrogen shift. 

The product hydrazide may be sulfonated and decomposed by heating with a base in ethylene glycol to yield benzaldehyde, CeHsCHO. Many aromatic aldehydes may be produced by similar routes. The hydrazone derivative of toluenesulfonic acid reacts with an aldehyde or a ketone in the presence of a base catalyst, such as sodium ethoxide, to yield the corresponding olefin (Bamford-Stevens reaction) ... 

The first step in the cycle, analogous to the cross-coupling reactions, is the oxidative addition of an aryl (vinyl) halide or sulfonate onto the low oxidation state metal, usually palladium(O). The second step is the coordination of the olefin followed by its insertion into the palladium-carbon bond (carbopalladation). In most cases palladium is preferentially attached to the sterically less hindered end of the carbon-carbon double bond. The product is released from the palladium in a / -hydrogen elimination and the active form of the catalyst is regenerated by the loss of HX in a reductive elimination step. To facilitate the process an equivalent amount of base is usually added to the reaction mixture. 

The reaction of an a-halo sulfone with a base to give an olefin is called the Ramberg-Backlund reaction.309 The reaction is quite general for a-halo sulfones with an a hydrogen, despite the unreactivity of a-halo sulfones in normal Sn2 reactions (p. 344). Halogen reactivity is in the order I > Br > Cl. Phase transfer catalysis has been used.310 In general, mixtures of cis and trans isomers are obtained, but usually the less stable cis isomer predominates. The mechanism involves formation of an episulfone and then elimination of... 

S02. There is much evidence for this mechanism,311 including the isolation of the episulfone intermediate,312 and the preparation of episulfones in other ways and the demonstration that they give olefins under the reaction conditions faster than the corresponding a-halo sulfones.313 Episulfones synthesized in other ways (e.g., 6-62) are reasonably stable compounds but eliminate S02 to give olefins when heated or treated with base. 

Alkylphenol. Alkylphenol is a common surfactant intermediate used to produce alkylphenol ethoxylates. Phenol reacts with an olefin thermally without a catalyst but with relatively poor yields. Catalysts for the reaction include sulfuric acid p-toluene sulfonic acid (PTSA), strong acid resins, and boron trifluoride (BF3). Of these, strong acid resins and BF3 are mostly widely used for the production of surfactant-grade alkylphenols. The most common alkylphenols are octylphenol, nonylphenol, and dodecylphe-nol. Mono nonylphenol (MNP) is by far the most common hydrophobe. It is produced by the alkylation of phenol with nonene under acid conditions. All commercially produced MNP is made with nonene based on propylene trimer. Because of the skeletal rearrangements that occur during propylene oligomerization, MNP is a complex mixture of branched isomers. 

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