Synthesis of indenones
In the presence of a rhodium catalyst, paraformaldehyde enables a CO gas-free carbonylative cyclization of alkynes with 2-bromophenylboronic acids to yield indenone derivatives. Rhodium-catalyzed decarbonylation of formaldehyde is followed by carbonylation of alkynes with 2-haloboronic acids, respectively, leading to efficient whole carbonylation.
T. Morimoto, K. Yamasaki, A. Hirano, K. Tsutusmi, N. Kagawa, K. Kakiuchi, Y. Harada, Y. Fukukomoto, N. Chatani, T. Nishioka, Org. Lett., 2009, 11, 1777-1780.
An iron-promoted oxidative tandem alkylation/cyclization of ynones with 4-alkyl-substituted 1,4-dihydropyridines provides 2-alkylated indenones with excellent selectivity under mild conditions. The process occurs via oxidative homolysis of a C-C σ-bond in 1,4-dihydropyridines to generate an alkyl radical followed by its addition to the C-C triple bond and an intramolecular cyclization.
F.-T. Xiong, B.-H. He, Y. Liu, Q. Zhou, J.-H. Fan, J. Org. Chem., 2022, 87, 8599-8610.
An efficient gold-catalyzed cyclization of 2-alkynylaldehyde cyclic acetals enables the synthesis of or a braod range of indenone derivatives in very good yields. The cyclic acetal group promotes a 1,5-H shift by activating the benzylic C-H bond and preventing the migration of the alkoxy group by tethering both alkoxy groups.
T. Yamada, K. Park, T. Tachikawa, A. Fujii, M. Rudoplf, A. S. K. Hashmi, H. Sajiki, Org. Lett., 2020, 22, 1883-1888.
A facile, efficient, and large-scale strategy for the synthesis of N-(1-Oxo-1H-inden-2-yl)benzamide derivatives via domino reaction between aryl aldehydes, hippuric acid, and acetic anhydride is catalyzed by HPW@nano-SiO2 under microwave irradiation. The reaction conditions are very simple and offer convenient isolation of the product. Moreover, the catalyst can be re-used up to five times after simple filtration.
M. Rostami, A. R. Khosropour, V. Mirkhani, I. Mohammadpoor-Baltork, M. Moghadam, S. Tangestaninejad, Synlett, 2011, 1677-1682.
An efficient rhodium-catalyzed C-H activation and multistep cascade reaction of benzimidates and alkenes enables the synthesis of diverse difunctionalized indenones in the presence of Mn(OAc)2. The transformation involves the cleavage and formation of multiple bonds in one pot under mild reaction conditions.
N. Lv, Z. Chen, Y. Liu, Z. Liu, Y. Zhang, Org. Lett., 2017, 19, 2588-2591.
One-pot tandem Meyer-Schuster rearrangement of arylpropynols and successive radical cyclization with disulfides enables the synthesis of 2-sulfenylindenone derivatives in good yields. The reaction tolerates a number of functional groups.
X.-S. Zhang, J.-Y. Jiao, X.-H. Zhang, B.-L. Hu, X.-G. Zhang, J. Org. Chem., 2016, 81, 5710-5716.
An electrooxidative direct arylsulfonlylation of ynones with sulfinic acids via a radical tandem cyclization strategy enables the construction of sulfonated indenones under oxidant-free conditions in very good yields. Notably, this reaction could be easily scaled up with good efficiency.
J. Wen, W. Shi, F. Zhang, D. Liu, S. Tang, H. Wang, X.-M. Lin, A. Lei, Org. Lett., 2017, 19, 3131-3134.