Heteroatom-directed metalation. Lithiation of N-propenylbenzamides and N-propenyl-o-toluamides. Novel routes to ortho-substituted primary benzamide derivatives and N-unsubstituted isoquinolin-1(2H)-ones
摘要:
Reaction of N-propenylbenzamides 4 and 9, obtained by LDA-induced isomerization of the corresponding N-allylbenzamides 1, 8, and 14, with 2 equiv of sec-butyllithium or tert-butyllithium at low temperature regiospecifically generates the highly reactive N,ortho-dilithiated species (e.g., 5 and 17). These dilithio species react avidly with a wide spectrum of electrophilic reagents, including alkyl halides, giving adducts which on hydrolysis with warm 50% aqueous acetic acid are converted into ortho-substituted primary benzamides in excellent yields. Ortho-lithiation of N-propenylbenzamides is thus formally equivalent to ortho-lithiation of primary benzamides themselves. The utility of this important, previously unknown, synthetic operation is enhanced by the well-known facility with which the primary amide moiety can be transformed into other useful functional groups, as exemplified by the synthesis of 2-methoxy-6-methylbenzoic acid (12) and 2-methoxy-6-methylbenzonitrile (13) from N-propenyl-2-methoxybenzamide (9), N-Propenyl-o-toluamide (7) undergoes regiospecific dilithiation on nitrogen and on the methyl group under conditions analogous to those used for the N-propenylbenzamides. These dilithio species react with DMF or "Weinreb type" amides to give condensation products which cyclize to N-propenylisoquinolin-1(2H)-ones under midly acidic conditions. Removal of the N-propenyl moiety under more strongly acidic conditions provides N-unsubstituted isoquinolin-1(2H)-ones with high overall efficiency. This process is exemplified by the synthesis of isoquinolin-1(2H)-one (23) and its 3-n-butyl congener 26 from N-propenyl-2-methylbenzamide (7).
A direct anionic cyclization of 2-alkynylbenzonitrile to 3-substituted-1(2H)-isoquinolones and 3-benzylideneisoindol-2-ones initiated by methoxide addition
作者:Ming-Jung Wu、Li-Juan Chang、Li-Mei Wei、Chi-Fong Lin
DOI:10.1016/s0040-4020(99)00812-1
日期:1999.11
2-(2-alkylethynyl)benzonitrile with sodium methoxide in refluxing methanol for 12 h gave 3-alkyl-1(2H)-isoquinolone in modest yield. Under the same reaction conditions, methanolysis of 2-(2-arylethynyl)benzonitrile lead to the formation of 3-alkylidene isoindol-1-one. Partial hydrolysis of 2-(1-hexynyl)benzonitrile to the corresponding benzamide, followed by treatment of the benzamide with sodium methoxide
3‐Oxo‐5‐alkynoic acid esters, on treatment with a carbophilic catalyst, undergo 6‐endo‐digcyclizationreactions to furnish either 2‐pyrones or 4‐pyrones in high yields. The regiochemical course can be dialed in by the proper choice of the alcohol part of the ester and the π‐acid. This transformation is compatible with a variety of acid‐sensitive groups as witnessed by a number of exigent applications
The hydration of o-ethynylbenzoic acid derivatives, such as ethyl o-ethynylbenzoate, o-ethynylbenzonitrile, and o-ethynylbenzamide, in sulfuric acid in the presence of marcuric sulfate, afforded 3-substituted isocoumarins. The palladium-catalyzed reaction of o-halobenzoic acid derivatives with terminal acetylenes to obstain the starting materials for the cyclization is also described.
Gold vs Rhodium Catalysis: Tuning Reactivity through Catalyst Control in the C–H Alkynylation of Isoquinolones
作者:Aslam C. Shaikh、Dinesh R. Shinde、Nitin T. Patil
DOI:10.1021/acs.orglett.6b00175
日期:2016.3.4
A site-selective C-4/C-8 alkynylation of isoquinolones catalyzed by gold and rhodium complexes is reported. A broad range of synthetically useful functional groups (−F, −Cl, −Br, −CF3, −OMe, alkyl, etc.) were tolerated, providing an efficient and robust protocol for the synthesis either C-4- or C-8-alkynylated isoquinolones.
Cobaltacycle synthesis via C–H activation has been achieved for the first time, providing key mechanisticinsight into cobalt catalytic chemistry. N-Chloroamides are used as a directing synthon for cobalt-catalyzed room-temperature C–H activation and construction of heterocycles. Alkynes as coupling partners allow convenient access to isoquinolones, a class of synthetically and pharmaceutically important