Methyl benzoate, acylation with

The synthesis of pyrazolines and pyrazoles of the [CCNN + C] type with the creation of two bonds, N(2)-C(3) + C(3)-C(4) (or N(l)-C(5) + C(5)-C(4)), has been studied by several groups. Beam and coworkers have published a series of papers on the synthetic utility of lithiated hydrazones. Thus, the methylhydrazone of acetophenone (598) is converted by butyllithium into the dianion (599), which in turn reacts with methyl benzoate to afford the pyrazole (600) (76SC5). In earlier publications Beam et al. have used aldehydes and acyl chlorides to obtain pyrazolines and pyrazoles by the same method. 

Pyrazylmethylsodium (20) has been reacted with a wide range of esters. Thus, reaction with methyl benzoate gives phenacylpyrazine in 95% yield. When the ester used for acylation is ethyl formate, bis(pyrazylmethyl)carbinol (24) is obtained instead of the expected pyrazylacetaldehyde (23).177... 

Dimethyl-188 and 2,6-dimethylpyrazine react very similarly to methylpyrazine. Thus, 2,6-dimethylpyrazine can be converted into a monoanion with sodamide in liquid ammonia which can be condensed with aldehydes and ketones,179 acylated with esters,181 and alkylated with alkyl halides181 to give the corresponding 2-methyl-6-substituted pyrazines. Acylation under suitable conditions also yields diacylated derivatives. Thus, when 2,6-dimethylpyrazine, sodamide, and ethyl benzoate are reacted in 1 3 2 molecular proportion, 38% 2,6-diphen-acylpyrazine (35) and 25% 2-methyl-6-phenacylpyrazine (36) is obtained. From the preparative point of view it is better to form the diacyl derivative by the further acylation of the monoacyl derivative rather than by direct diacylation.187... 

Trimesitylplumbyllithium, generated by reaction of hexamesityldiplumbane with lithium, reacts with acyl chlorides to afford isolable air-stable acylplumbanes in modest yields (Equation (127)). Under ultraviolet irradiation as well as thermal decomposition, the benzoylplumbane reacted with methanol to afford methyl benzoate (Equation (128)).156 The simpler acetyl- and benzoyl-triphenylplumbane were only detected as transient species in solution, the acetyltriphenylplumbane decomposing at 50 °C to give acetophenone.157... 

Compound 16 has been syntheased [52] as described in the Scheme T. Methyl-amino benzoate 16a reacts with diethyl bromomalonate to give 16b, which has been acylated with 3-bromo propionic acid and PCI3 to provide 16c. 

The acylation of the pinacol derivative of dihydTOxy[lithio(trimethylsilyl)methyl]borane with methyl benzoate has been recoided, No details were given due to difficulties in the isolation of the products. 

Acylation of Mes2BCHzLi (2) with methyl benzoate for 5 min gave a 72% yield of acetophenone, marginally better than for use of benzoyl cMoride or benzoic anhydride. However, acylation of other dimesitylboryl-stabilized anions does not appear to be of general use, often giving only modest yields. The ethoxycarbonylation shown in equation (38) leads to ethyl octanoate in 50% yield. When dimethyl carbonate was used, a-methylation occurred in preference to ester homologation. ... 

Usually the C-0 single bond in esters is cleaved at the acyl-0 bond, whereas examples of cleavage at the other point in esters have been reported. An electron-rich iron(O) complex produced on reductive elimination of naphthalene from a hydrido(naphthyl)iron complex undergoes oxidative addition reaction with methyl benzoate to give a methyliron benzoate complex (Eq. 22) [63]. 

Under the same basic conditions /ra . -l-acetoxymethyl-1-methyl-2-tosylcyclopropane generated an a-sulfonyl anion, which attacked the ester group intramolecularly and afforded 2,5-dimethyl-l-tosyl-3-oxabicyclo[3.1.0]hexan-2-ol (22) in 50% yield.Stereoselective synthesis with a chiral cyclopropyl sulfoxide was experienced when ( )-4-tolylsulfinylcyclopropane was reacted first with butyllithium and then with methyl benzoate and gave 1-benzoyl-1-[(5)-4-tolylsulfinyl]cyclopropane (23a) in 62% yield. A useful reaction took place when 2-(hy-droxymethyl)cyclopropyl phenyl sulfide was treated first with an excess of butyllithium and then with dimethylformamide and gave 2-hydroxy-l-phenylsulfanyl-3-oxabicyclo[3.1.0]hexane (24), a lactol which has been used to carry out various useful synthetic transformations. Another useful reaction occurred when cyclopropyl phenyl sulfones were treated with butyllithium followed by an acyl imidazole to give acyl cyclopropanes in decent yield. 

C(l)-Phenyl-substituted alkenyloxyboranes (13) may be prepared by the acylation of boron-stabilized carbanions with methyl benzoate (Scheme 12). ... 

Hwang, J. P., Prakash, G. K. S., and Olah, G. A. 2000. Trifluoromethanesulfonic acid catalyzed novel Friedel-Crafts acylation of aromatics with methyl benzoate. Tetrahedron 56 7199-7203. 

Methyl- and 2,3-dimethylquinoxalines have been acylated with benzoate, trifluoroacetate, oxalate, and phthalate esters using sodium hydride as the condensing agent. Both mono- and diacyl derivatives are obtained from 2,3-dimethylquinoxaline with excess of methyl benzoate and diethyl oxalate the products 55 and 56 are obtained, respectively. Compound 57 is produced by condensation of the dimethyl compound with diethyl phthalate. ... 

Triflic acid-catalyzed Friedel-Crafts acylation reactions of aromatics with methyl benzoate give benzophenone products in good to excellent yields (eq 33). To explain the high level of electrophilic reactivity of this system, protosolvated species are proposed as possible intermediates (eq 32). In the triflic acid-catalyzed cyclization of some ethylene dications, protonation of the ester group is thought to be a key activation step. Reaction of a-(methoxycarbonyl)diphenylmethanol with TfOH gives the fluorene product in 94% yield (eq 34). ... 

Preparation by acylation of o-cresol with p-(trichloro-methyl)phenyl p-(trichloro-methyl)benzoate in methylene chloride in the presence of aluminium chloride at 0-5° over 1 h, then at r.t. for 1 h, followed by alkaline hydrolysis of the resnlting keto ester [325] (Japanese patent). 

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