Propargylic compounds carbonylation

Acceptor-substituted allenes can be prepared from the corresponding propargyl precursors by prototropic isomerization (see Section 7.2.2). Conversely, such allenes can also be used to synthesize propargyl compounds. For example, treatment of the sulfoxides 417 with 1 equivalent of a lithiation reagent leads to the intermediates 418, which furnish propargyl sulfoxides 419 by hydrolysis (Scheme 7.55) [101]. If the electrophiles used are not protons but primary alkyl halides or carbonyl compounds, the products 420 or 421, respectively, are formed by C,C linkage. 

Allenic esters can be generated by palladium-catalyzed carbonylation of propargyl compounds (see Section 7.2.6). Under the reaction conditions applied, however, succeeding reactions occur directly in many cases, for instance by introduction of a second ester function. Many examples of such carbonylation reactions of allenic esters were summarized in a review by Tsuji and Mandai [136],... 

Propargylic compounds undergo facile Pd-catalysed mono- and di-carbonylations depending on the reaction conditions [6]. The facile monocarbonylation of propargylic... 

Propargylic compounds undergo facile palladium-catalyzed mono- and dicarbonylations, depending on the reaction conditions [9]. The carbonylation of propargylic alcohols has... 

Allylations, allenylations, and propargylations compounds in aqueous media can also be carried out with preformed organic tin reagent, rather than the use of metals.For example, the allylation reaction of a wide variety of carbonyl compounds with tetraal-lyltin was successfully carried out in aqueous media by using scandium trifluoromethanesulfonate (scandium inflate) as a catalyst (Eq. 8.40). A phase-transfer catalyst (PTC) was found to help the allylation mediated by tin at room temperature without any other assistance. ... 

Soon afterwards, the same group developed methodologies for the oxidative carbonylation of 4-yn-l-ones and propargylic esters (Scheme 8.22). While 2-cyclopentenone carboxylates were obtained from appropriate carbonyl-substituted alkynes [96], cyclic orthoesters and furanones were successfully synthesized starting from corresponding propargylic compounds [97]. More recently, they also realized the asymmetric version of this reaction [98], which has also been applied in the total synthesis of (—)-AL-2 by Mukai and Miyakoshi [99]. 

Palladium-catalyzed carbonylation of allylic and propargylic compounds offers a potential tool of one-carbon homologation. Particularly, pd-catalyzed carbonylation of propargylic compounds further provides synthetically valuable transformations because of the high reactivity of the intermediary allenyl esters. 

J. Tsuji and J. Kiji, in Transition Metals for Organic Synthesis, Vol. 1, M. Beller and C. Bolm, Eds., Wiley-VCH, Weinheim, 1998, 68-78. Palladium-Catalyzed Carbonylation of Allylic and Propargylic Compounds. 

Although superficially similar, propargyl compounds do not form t -complex intermediates, but give t -allenic complexes. As part of a catalytic cycle, these can undergo typical reactions, such as coupling (Schemes 9.82 and 9.83), ° ° reduction by formate, alkene insertion and carbonylation (Scheme 9.84). 

The allenyl moiety (2,3-aikadienyl system) in the carbonylation products is a reactive system and further reactions such as intramolecular Diels-Alder and ene reactions are possible by introducing another double bond at suitable positions of the starting 2-alkynyl carbonates. For example, the propargylic carbonate 33 which has l,8(or 1.9)-diene-3-yne system undergoes tandem carbonylation and intramolecular Diels-Alder reaction to afford the polycyclic compound 34 under mild conditions (60 C, 1 atm). The use of dppp as ligand is important. One of the double bonds of the allenyl ester behaves as part of the dieneflSj. 

Acetylene is condensed with carbonyl compounds to give a wide variety of products, some of which are the substrates for the preparation of families of derivatives. The most commercially significant reaction is the condensation of acetylene with formaldehyde. The reaction does not proceed well with base catalysis which works well with other carbonyl compounds and it was discovered by Reppe (33) that acetylene under pressure (304 kPa (3 atm), or above) reacts smoothly with formaldehyde at 100°C in the presence of a copper acetyUde complex catalyst. The reaction can be controlled to give either propargyl alcohol or butynediol (see Acetylene-DERIVED chemicals). 2-Butyne-l,4-diol, its hydroxyethyl ethers, and propargyl alcohol are used as corrosion inhibitors. 2,3-Dibromo-2-butene-l,4-diol is used as a flame retardant in polyurethane and other polymer systems (see Bromine compounds Elame retardants). 

In synthetic applications, Li et al. examined the propargylation-allenylation of carbonyl compounds by using a variety of metals including Sn, Zn, Bi, Cd, and In.203 By using the indium-mediated allenylation reaction, Li and co-workers developed the synthesis of the antiviral, antitumor compound (+)-goniofufurone (Scheme 8.22),204 a key component isolated from the Asian trees of the genus Goniothalamus,205 and other styryl lactone derivatives (Eq. 8.80). 

Deprotection of 2,2-disubstituted-l,3-dithiolanes to give carbonyl compounds can be achieved using Oxone with KBr in aq. MeCN <06TL8559> and a review of silylated heterocycles as formyl anion equivalents includes reference to 64 <06CC4881>. A method for transformation of propargylic dithiolanes 43 into tetrasubstituted furans has been reported <06SL1209> and Michael addition of enolates to the chiral dithiolane dioxide 65 takes place... 

Air-stable palladium(O) catalyst, [(Cy3P)2Pd(H)(H20)]BF4, catalyses carbonylation of propargylic alcohols to generate dienoic acids and esters (equation 167)286. Since propar-gyl alcohols are obtained from carbonyl compounds by acetyhde addition reactions, this sequence constitutes a three-carbon homologation. a-Allenic alcohols are converted to tt-vinylacrylic acids under similar conditions (equation 168)287. 

Muller and co-workers reported the three-component one-pot synthesis of various pyrimidines through the in situ generation of unsaturated carbonyl compounds. The palladium catalyzed coupling of aryl halides bearing electron withdrawing substituents 7 with propargyl alcohols 8 produced unsaturated carbonyl compounds 9 after isomerization, which condensed with amidines 10 to form triaryl pyrimidines 11 . 

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