3- benzoic acid reaction with alkynes

Reactions with alkynes may lead to the formation of cyclized products. The reaction of iodobenzenes with two equivalents of an alkyne has been shown to give naphthalene derivatives in the presence of cobalt catalyst with a manganese reduc-tant. The process, shown in Scheme 15, is thought to involve oxidative addition of the aryliodide to cobalt followed by double alkyne insertion. The cobalt-catalysed annulation step probably involves an pathway. The cyclopentadienyl-rhodium-catalysed annulation of benzoic acids with alkynes has been used to form isocoumarin derivatives, such as (126). The process is thought to involve cyclorhodation at the ortho-position of a rhodium benzoate intermediate, followed by alkyne insertion to form a seven-membered rhodacycle and reductive elimination The silver-catalysed annulations of diphenylphosphine oxides with alkynes proceed in the absence of rhodium. Benzophosphole oxides such as (127), formed with diphenylethyne, are produced. Here, the proposed mechanism involves homolytic cleavage of the phosphorus-hydrogen bond to give a radical which can add to the alkyne and subsequently cyclize. ... 

In a remarkable reaction according to Eq. 18 palladium(II) acetate reacts in methanol with diphenylacetylene to form dinuclear [Pd(T 5-C5Ph5)]2(p-PhC = CPh) (67) [79], The reaction mechanism was studied in some detail and part of the alkyne molecule was found as benzoic acid orthoester PhC(OMe)3. When... 

A rapid MW-assisted palladium-catalyzed coupling of heteroaryl and aryl boronic acids with iodo- and bromo-substituted benzoic acids, anchored on TentaGel has been achieved [174]. An environmentally friendly Suzuki cross-coupling reaction has been developed that uses polyethylene glycol (PEG) as the reaction medium and palladium chloride as a catalyst [175]. A solventless Suzuki coupling has also been reported on palladium-doped alumina in the presence of potassium fluoride as a base [176], This approach has been extended to Sonogashira coupling reaction wherein terminal alkynes couple readily with aryl or alkenyl iodides on palladium-doped alumina in the presence of triphenylphosphine and cuprous iodide (Scheme 6.52) [177]. 

Insertion of aUcynes into aromatic C-H bonds has been achieved by iridium complexes. Shibata and coworkers found that the cationic complex [Ir(COD)2]BF4 catalyzes the hydroarylation of internal alkynes with aryl ketones in the presence of BINAP (24) [111]. The reaction selectively produces ort/to-substituted alkenated-aryl products. Styrene and norbomene were also found to undergo hydroarylation under similar condition. [Cp IrCl2]2 catalyzes aromatization of benzoic acid with two equivalents of internal alkyne to form naphthalene derivatives via decarboxylation in the presence of Ag2C03 as an oxidant (25) [112]. 

In fact, the addition of 1,4-dimethoxybenzene (DMB) and/or several similar compounds, at concentrations as low as 10 4 M, to a mixture of aryl-olefins and DCA almost completely inhibits the reactions. Concentration dependence and flash photolysis studies confirm that the primary electron-transfer process occurs between the singlet excited sensitizer and DMB (E01 = 1.34 V vs SCE) with the generation of the corresponding radical ion pair. As a consequence, quantum yields lower than 1, even at infinite substrate concentration, are measured [95]. In this regard, valuable confirmations came from the cyanoaromatic photoinduced electron-transfer oxygenation of alkynes [99], Farid and Mattes reported that the photooxygenation of diphenylacetylene DPA (E° = 1.85 V vs SCE) 25, leading to a mixture of benzil 26 and benzoic acid 27, was efficiently sensitized by DCA ( = 0.15), but poorly by TCA ( > < 0.001) [Eq. (12)] [99]. 

For the Pauson-Khand [2+2+1] cycloaddition175 of alkyne, alkene, and carbon monoxide, as well as being promoted by Co2(CO)8, Portnoy et al.176 synthesized a dendronized support modified with 2- and 4-(diphenylphosphino)benzoic acid groups Co2(CO)8 was then incorporated into the support. A notable increase in catalytic activity and selectivity for the intramolecular Pauson-Khand reaction was found for the Co complexes immobilized on the second-and third-generation dendron-functionalized polystyrene, when compared with the analogous nondendronized support. 

While enynes are common products in the reaction of 1-alkynes under Wilkinson s catalyst, hydrative dimerization products of 1-alkyne with H2O are obtained in the presence of an additional cocatalyst, 2-amino-3-picoline. For instance, when the reaction of terminal alkynes and FI2O is carried out using the catalytic system of RhCl(PPh3)3, 2-amino-3-picoline, and benzoic acid in THF, a mixture of branched a,/3-enone and linear enone can be obtained in a 4 1 ratio (eq 81). ... 

Phenyl-1-propyne (55) underwent facile formal intermolecular hydroamination, affording the allylic amine 56 in high yield at 0 "C in the presence of AcOH or benzoic acid. In this reaction, at first, Pd-catalyzed isomerization of 55 to pheny-lallene (57) occurs by addition-elimination of H-Pd-OAc to internal alkyne 55, and then the allene 57 is converted to jr-allylpalladium intermediate 58 by hydropal-ladation. The final step is a well-known amination to produce the allylic amine 56. As an intramolecular version, 2-(2-phenylpropenyl)pyrrole (60) was obtained from l-phenyl-7-amino-l-hexyne 59 [16,16a]. Similarly Pd/benzoic acid-catalyzed hydroalkoxylation of 55 with (—)-menthol (61) afforded the allylic ether 62 [17]. 

Aromaticity is one of the most fascinating popular qualitative chemical concepts in chemistry Michael Faraday isolated benzene by distillation in 1825. He noticed that although benzene is an unsaturated compound with H C 1 1 it is much less reactive than the related unsaturated aliphatic compounds. Moreover, it undergoes substitution reactions rather than addition reactions exhibited by alkenes and alkynes. Eilhard Mitscherlich synthesized benzene by heating benzoic acid with lime. 

Benzoic acids are convenient entry points for this chemistry as they can be converted in a one-pot reaction into an O-methyl hydroxamates [81] This reaction has been developed using rhodium complexes as catalysts and O-methyl hydroxamates as the substrates along with an internal alkyne [81]... 

In 2007, Ueura et al. reported the first effective example for oxidative coupling of aromatic substrates with alkynes through C—H bond cleavage under rhodium catalysis [22]. Thus, benzoic acids 9 and 50 react with alkynes 2 efficiently in the presence of 0.5 mol % of [Cp RhCl2]2 and 2 equiv of Cu(OAc)2 H2O in o-xylene at 100 °C to afford the corresponding isocoumarins 51 as 1 1 coupling products (Scheme 25.26) [5,22]. Five years later, the same reaction was conducted using ruthenium catalysts in place ofRh [23]. 

In 2007, the Mlura group reported a Rh(III)-catalyzed oxidative coupling of benzoic acids with internal alkynes to the synthesis of isocoumarins via aromatic C-H activation (Scheme 6.24a) [38]. Importantly, the reaction of benzoic acids with alkynes takes place efficiently even with a reduced amount (5mol%) of Cu(0Ac)2-H20 under air (Scheme 6.24b) [5b]. The same group also developed the rhodium-catalyzed coupling of acrylic acids with alkynes to provide corresponding a-pyrone via vinylic C-H bond cleavage (Scheme 6.24c) [5c]. In 2015, Wen and coworkers described a Rh(III)-catalyzed synthesis of... 

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