Synthesis of Isocoumarins
An efficient and robust palladium-catalyzed nucleophilic addition/oxidative annulation of bromoalkynes with benzoic acids provides 3-substituted isocoumarins.
G. Jiang, J. Li, C. Zhu, W. Wu, H. Jiang, Org. Lett., 2017, 19, 4440-4443.
A copper-catalyzed tandem C-C/C-O coupling strategy from readily available 2-iodo-N-phenyl benzamides and acyclic diketones as starting materials enables a facile and rapid synthesis of isocoumarin derivatives.
V. Kavala, C.-C. Wang, D. K. Barange, C.-W. Kuo, P.-M. Lei, C.-F. Yao, J. Org. Chem., 2012, 77, 5022-5029.
An efficient strategy for the synthesis of a variety of 3-substituted isocoumarins in very good yields proceeds from o-halobenzoic acids and 1,3-diketones via a copper(I)-catalyzed domino reaction in DMF under the action of K3PO4 at 90-120°C without a ligand.
S. Cai, F. Wang, C. Xi, J. Org. Chem., 2012, 77, 2331-2336.
A palladium-catalyzed α-arylation step followed by an intramolecular cyclization process enables the preparation of various isocoumarins directly from 2-halobenzoates and ketones. In case of 2-bromobenzoates, the addition of iodide anions to the reaction mixture increased yields and selectivities. This phosphine-free one-pot synthesis features a high functional group tolerance and gives access to richly decorated isocoumarins.
A. Casnati, R. Maggi, G. Maestri, N. Della Ca', E. Motti, J. Org. Chem., 2017, 82, 8296-8303.
A highly efficient palladium(0)-catalyzed strategy for the synthesis of isocoumarins involves cyclization with incorporation of tert-butyl isocyanide followed by simple acid hydrolysis to provide valuable lactones in good yields. The methodology is tolerant of a wide range of substrates and applicable to library synthesis.
X.-D. Fei, Z.-Y. Ge, T. Tang, Y.-M. Zhu, S.-J. Ji, J. Org. Chem., 2012, 77, 10321-10328.
A simple and highly efficient strategy for the synthesis of 3-substituted isocoumarins from 1-(2-halophenyl)-1,3-diones is based on a cascade copper(I)-catalyzed intramolecular Ullmann-type C-arylation and rearrangement process. This methodology tolerates a wide range of substrates and is applicable to library synthesis.
Z.-Y. Ge, X.-D. Fei, T. Tang, Y.-M. Zhu, J.-K. Shen, J. Org. Chem., 2012, 77, 5736-5743.
p-Toluenesulfonic acid (PTSA) in ethanol was used as a mild acid catalyst for the annulation of various functionalized diarylalkynes under microwave irradiation. This metal-free process allowed the synthesis of various 3-aryl-substituted isocoumarins in good yields.
G. Le Bras, A. Hamze, S. Messaoudi, O. Provot, P.-B. Le Calvez, J.-D. Brion, M. Alami, Synthesis, 2008, 1607-1611.
Addition of a catalytic amount of Cy2NH·HX improves the rate and yields for cyclization reactions of o-(alkynyl)benzoates in the presence of a stoichiometric amount of copper(II)halide to give 4-haloisocoumarins. Under the standard reaction conditions, various 4-haloisocoumarins are provided in good yield.
Y. Liang, Y.-X. Xie, J.-H. Li, Synthesis, 2007, 400-406.
A simple addition of o-halobenzoic acids to active internal alkynes proceeds efficiently in the presence of CuCl2 as a catalyst to give the corresponding isocoumarin derivatives.
X.-X. Guo, J. Org. Chem., 2013, 78, 1660-1664.