Alkyne To aldehyde

The chemistry oudined in Schemes 12 and 13 has been developed to provide a mild mediod for die conversion of aldehydes to alkynes via vinylstannanes as intermediates, and moderately complex... 

Villieras, J., Perriot, P, and Normant, J.F., Simple route from aldehydes to alkynes and 1-chloro-l-alkynes. Synthesis, 458, 1975. 

Decarbonylation of the acylmetal intermediates has been extended to a variety of carbon-carbon forming reactions. For example, Li et al. reported decarbonylative addition reactions of aromatic aldehydes to alkynes (Scheme 7.17) [24] and acrylates [25]. An oxidative decarbonylative coupling reaction of aromatic aldehydes with 2-arylpyridines was promoted by a rhodium catalyst (Scheme 7.18) [26]. Carboxylic acid derivatives were also employed for analogous carbon-carbon bond-forming reactions through decarbonylation [27]. 

Hayashi A, Yamaguchi M, Hirama M. SbFs-promoted addition of aldehydes to alkynes. Synlett 1995 195-1%. 

Diaryl disulfides and diselenides add to alkynes to afford the (Z)-l, 2-bis(ar-ylthio)alkenes 193 and (Z)-l,2-bis(arylseleno)alkenes 194. Under CO pressure, carbonylative addition takes place to give thio esters and the selenoketones 195[I07], The selenoketones are converted into the /J-seleno-a, 3-unsaturated aldehydes 196 by Pd-catalyzed hydrogenolysis with HSnBu3[108,109],... 

Sulfitation and Bisulfitation of Unsaturated Hydrocarbons. Sulfites and bisulfites react with compounds such as olefins, epoxides, aldehydes, ketones, alkynes, a2iridines, and episulftdes to give aHphatic sulfonates or hydroxysulfonates. These compounds can be used as intermediates in the synthesis of a variety of organic compounds. 

Reactions between aldehydes and alkynes to give propargyl alcohols are also described in Kitazume and Kasai s paper [55]. Here, various aldehydes such as benzaldehyde or 4-fluorobenzaldehyde were treated with alkynes such as phenylethyne or pent-l-yne in three ionic liquids [EDBU][OTf], [BMIM][PFg], and [BMIM][BF4] (Scheme 5.1-27). A base (DBU) and Zn(OTf)2 were required for the reaction to be effective the yields were in the 50-70 % range. The best ionic liquid for this reaction depended on the individual reaction. 

Scheme 5.1-27 The zinc triflate-catalyzed coupling of alkynes with aldehydes to give propargyl alcohols in an ionic liquid.

Enamines can also be converted to amino alcohols via hydroboration. Allene-boranes react with aldehydes to give alkyne-alcohols. ... 

Similar reactions have been carried out on acetylene. Aldehydes add to alkynes in the presence of a rhodium catalyst to give conjugated ketones. In a cyclic version of the addition of aldehydes, 4-pentenal was converted to cyclopen-tanone with a rhodium-complex catalyst. In the presence of a palladium catalyst, a tosylamide group added to an alkene unit to generate A-tosylpyrrolidine derivatives. ... 

Addition of carboxylic acids to alkynes Acylation of aldehydes or ketones Bisdecarboxylation of malonic acids Oxidation of arylmethanes with CrOs and AC2O... 

Addition of alcohols or phenols to alkynes addition of aldehydes or... 

The cycloaddition of alkynes with the tributylphosphine-carbondisulfide adduct 131 results in the in situ formation of the ylides 132 which react with aldehydes to give the novel 2-arylidene or 2-alkylidene-l,3-dithioles 133 (Scheme 36) [132]. Concerning ylides C-substituted by sulfur we can also mention a publication on the behavior of various keto-stabilized ylides towards acyclic and cyclic a s-disulfides allowing the synthesis of substituted thiazoles, thiols, and dithiols [133]. 

As in the P(III) chemistry above, both late metal (Pd) and lanthanide catalysts have been used for P(V)-H additions to alkynes, alkenes, aldehydes, and imines. In addition, titanium, aluminum, and zinc catalysts have been employed. Typical P(V) substrates include dialkyl phosphites P(0R)2(0)H and phosphine oxides PR2(0)H. 

The addition of allyl alcohol to alkynes to form y,8-unsaturated ketones and aldehydes (Eq. 3.46) in aqueous media was developed by both Trost and Dixneuf.182... 

The combination of Ni(COD)2/NHC complexes with EtaSiH as the reducing agent has also proved to be effective in inter molecular couplings of aldehydes and alkynes (Scheme 9) [21]. A broad range of substrates underwent couplings, including aromatic, non-aromatic, and terminal alkynes as well as branched, unbranched, and aromatic aldehydes. The regioselectivity with... 

A number of chiral monodentate phosphines have been examined in asymmetric nickel-catalyzed reductive couplings of aldehydes and alkynes. The best results to date have been obtained with (+)-NMDPP (16) [33]. Aromatic internal alkynes and branched aldehydes participate with excellent enantiose-lectivity (Scheme 15), although yields and enantioselectivities were somewhat lower with other combinations of aldehydes and alkynes. In a complemen-... 

The initially proposed mechanism [14], and one that continues to be considered as the likely pathway for most variants, involves the oxidative cyclization of a Ni(0) complex of an aldehyde and alkyne to a metallacycle (Scheme 18). Metallacycle formation could proceed independently of the reducing agent via metallacycle 19, or alternatively, metallacycle 20a or 20b could be formed via promotion of the oxidative cyclization transformation by the reducing agent. Cleavage of the nickel-oxygen bond in a o-bond metathesis process generates an alkenyl nickel intermediate 21. In the variants involv-... 

The mechanism of [3 + 2] reductive cycloadditions clearly is more complex than other aldehyde/alkyne couplings since additional bonds are formed in the process. The catalytic reductive [3 + 2] cycloaddition process likely proceeds via the intermediacy of metallacycle 29, followed by enolate protonation to afford vinyl nickel species 30, alkenyl addition to the aldehyde to afford nickel alkoxide 31, and reduction of the Ni(II) alkoxide 31 back to the catalytically active Ni(0) species by Et3B (Scheme 23). In an intramolecular case, metallacycle 29 was isolated, fully characterized, and illustrated to undergo [3 + 2] reductive cycloaddition upon exposure to methanol [45]. Related pathways have recently been described involving cobalt-catalyzed reductive cyclo additions of enones and allenes [46], suggesting that this novel mechanism may be general for a variety of metals and substrate combinations. 

A variety of alternate methods for the reductive coupling of aldehydes and alkynes have been developed. A number of important hydrometallative strategies have been developed, although most of these methods require the stoichiometric formation of a vinyl metal species or metallacycle. A very attractive hydrogenative coupling method has recently been developed, and its scope is largely complementary to the nickel-catalyzed methods. A very brief overview of these methods is provided below. 

Besides isocyanides, Nair and coworkers also used carbenes to add to alkynes such as DMAD (9-90) leading to 1,3-dipoles, which can be trapped in a formal 1,3-dipolar cycloaddition (Scheme 9.21) [61]. Thus, the dimethoxycarbene 9-99, generated in situ through thermolysis of 9-98, reacts with DMAD (9-90) to give the dipole 9-100, which adds to an aldehyde 9-97 or a ketone. As the final product, dihydrofurans 9-101 are obtained in good yields. 

Interaction of a carbonyl group with an electrophilic metal carbene would be expected to lead to a carbonyl ylide. In fact, such compounds have been isolated in recent years 14) the strategy comprises intramolecular generation of a carbonyl ylide whose substituent pattern guarantees efficient stabilization of the dipolar electronic structure. The highly reactive 1,3-dipolar species are usually characterized by [3 + 2] cycloaddition to alkynes and activated alkenes. Furthermore, cycloaddition to ketones and aldehydes has been reported for l-methoxy-2-benzopyrylium-4-olate 286, which was generated by Cu(acac)2-catalyzed decomposition of o-methoxycarbonyl-m-diazoacetophenone 285 2681... 

Tantalum(v) chloride can be used in the generation of 72-alkyne complexes (general formula 118) which have been shown to react with aldehydes to afford, after basic aqueous workup, allylic alcohols 119 (Scheme 50).180... 

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