Functionalized chromen-5-ones

J. Kamalraja, D. Muralidharan, P. T. Perumal, Synlett 2012, 23, 2894—2898. An efficient, one-pot regioselective synthesis of highly functionalized chromene-5-ones and pyrano[3,2-c] chromene-5-ones via a tandem Knoevenagel-Michael-cycli-zation sequence. 

M. S. Singh, G. C. Nandi, S. Samai, Green Chem. 2012, 14, 447 55. DABCO-promoted three-component legioselective synthesis of functionalized chromen-5-ones andpyrano[3,2-c] chromen-5-ones via direct annulation of a-oxoketene-lV,5-arylaminoacetals under solvent-free conditions. 

Chromones (4f -chromen -ones, 4//-l-benzopyran-4-ones) are naturally occurring oxygen-containing heterocycles which perform important biological functions in nature [46]. Many chromone derivatives, including flavones and 2-(trifluoromethyl)... 

Multiple sequential functionalizations of pyryliums with silyl enol ethers gives rise to a variety of products, including tetrahydro-2/f-chromenes and dicyclopenta[r ,/]octahydroxanthen-9-ones, as shown in the tables below (Schemes 8 and 9) <2001AGE568>. 

The use of coumarin in Diels-Alder reactions is, by comparison to pyran-2-ones, still largely unexplored. This is likely due to the low reactivity of the double bond at positions 3 and 4. Diels-Alder reactions with 3-substituted coumarins are rare, despite the potential to synthesize tetrahydro-6//-benzo[c]chromen-6-ones, important precursors to functionalized biphenyls and several natural products. Electron-withdrawing substitution at C-3 does not serve to efficiently activate the dienophilic system thus, it has been found that high temperatures and pressures are necessary to effect the reaction (e.g., Equation 25) <2006JOC70>. 

Chen L, Huang XJ, Li YQ, Zhou MY, Zheng WJ (2009) A one-pot multicomponent reaction for the synthesis of 2-amino-2-chromenes promoted by N, N-dimethylamino-functionalized basic ionic liquid catalysis under solvent-free condition. Monatsh fUr Chem 140 45 7... 

Monteiro and co-workers recently used this approach in their synthesis of 2,3-disubstituted furocoumarins. These compounds have proven to be important functional components with a host of interesting biological properties. Cycloisomeratization of 4-methoxy-3-(phenylethynyl)-2i/-chromen-2-one with methyl iodide in the presence of palladium tetraphenylphosphine in DMF gave the corresponding 2-aryl-3-alkyl furocomarin in modest yield. This approach was also employed by Cheng and Hu in their synthesis of substituted furocoumarins. ... 

Mondal et al. reported the synthesis of a new robust, non-air-sensitive, metal-free triazine-functionalized mesoporous organocatalyst TFMO-1 (Figure 1.5) and successfully used this material as an excellent catalyst in the one-pot three-component condensation reactions for the syntheses of 2-amino-chromene derivatives under solvent-free conditions (Mondal et al., 2012). TFMO-1 is an easily separable heterogeneous organocatalyst devoid of metal ions and thus is highly desirable to address industrial and environmental concerns. 

Mondal, 1., Modak, A., Nandi, M., Uyama, H., Bhaumik, A. 2012. Triazine functionalized ordered mesoporous organosiUca as a novel organocatalyst for the facile one-pot synthesis of 2-amino-47/-chromenes under solvent-free conditions. RSC Advances 2(30) 11306-11317. 

Shaabani, A., Ghadari, R., Ghasemi, S., Pedarpour, M., Rezayan, A.H., Sarvary, A., Ng, S.W. 2009. Novel one-pot three- and pseudo-five-component reactions Synthesis of functionalized benzo[g]- and dihydropyrano[2,3-g]chromene derivatives. Journal of Combinatorial Chemistry ll(6) 956-959. 

The reaction started with the tandem oxa-Michael-Michael reaction of 83 and 84 to give 87 in 76% yield and greater than 99% ee. The following Michael-aldol condensation with 4,4-dimethoxy-but-2-enal 85 works nicely in 69% yield and also excellent enantioselectivity. The obtained hexahydro-6//-benzo[c]chromene 88 is a highly functionalized intermediate in the total synthesis of (+)-conicol 89. The two-step reaction could be achieved in one pot from 83 and 84, without isolation of the intermediate 87, with a 55% overall isolated yield of 88. 

Keywords Isocyanides, dialkyl acetylenedicarboxylates, 2,5-dihydroxycyclohexa-2,5-diene-1,4-dione, 2-hydroxynaphthalene-l,4-di(Mie, acetonitrile, room temperature, one-pot multi-component synthesis, functionalized hfs(47/-chromeme) and 4//-benzo[g]chromene derivatives... 

Brahmachari, G., and Laskar, S. (2014). Nano-MgO-catalyzed one-pot synthesis of phosphonate ester functionalized 2-amino-3-cyano-4//-chromene scaffolds at room temperature. Phosphorus, Sulfur, and Silicon and the Related Elements, 189, 873-888. 

The function of Co (salpr)(OH) as a base under neutral conditions has been demonstrated in the following reactions (1) conversion of 2 -hydroxychalcones to flavanones in methanol [87], (2) retro-Claisen reaction of l-(2-hydroxyphenyl)-3-phenyl-1,3-propanediones in methanol [88], (3) the synthesis of 4ff-Chromen-4-ones from l-(2-hydroxyphenyl)-l,3-propanediones in 2,2,2-trifluoroethanol [89], (4) highly selective formation of a-Aryl-a-hydroxyacetic esters from arylglyoxals in an alcohol [90] and (5) the reaction of dibenzoylmethanes with formaldehyde to give 1,1,3,3,-tetrabenzoyl-propanes in dichloromethane [91]. 

Iaroshenko VO, Savych I, VUlinger A, Sosnovskikh VY, Langer P (2012) Reactions of 3-acylchromones with dimethyl 1,3-acetonedicarboxylate and 1,3-diphenylacetone one-pot synthesis of functionalized 2-hydroxybenzophenones, 6i/-benzo[c]chromenes and benzo[c] coumarins. Org Biomol Chem 10 9344-9348... 

G. Zhang, Y. Zhang, J. Yan, R. Chen, S. Wang, Y. Ma, R. Wang, One-pot enantioselective synthesis of functionalized pyranocoumarins and 2-amino-4H-chromenes discovery of a type of potent antibacterial agent, J. Org. Chem. 77 (2012) 878-888. 

M. Mirza-Aghayan, S. Nazmdeh, R. Boukherroub, M. Rahimifard, A.A. Tarlani, M. Abolghasemi-Malakshah, Convenient and efficient one-pot method for the synthesis of 2-amino-tetrahydro-4H-chromenes and 2-amino-4H-benzo[/ ]-chromenes using catalytic amount of amino functionalized MCM-41 in aqueous media, Synth. Commun. 43 (2013) 1499-1507. 

Scheme 9.36 Synthesis of Benzo[c]chromen-6-ones by C-H functionalization/C-O Cydiza-tion.

Ison and coworkers reported that the formation of 2-hydroxy-6//-benzo[c] chromen-6-ones can be achieved by C-H bond functionalization of benzoic acid [152]. In a typical example, the benzoic acid (lequiv.) was reacted with benzoquinone (2 equiv.) in the presence of NaOAc (2 equiv.) and a catalytic amount (10mol%) of [Cp IrCl2]2 in toluene at 120°C for 24h and gave 2-hydroxy-6/f-benzo[c]chromen-6-one in 83% yield (Scheme 11.4). 

Thakrar et al. (2013) synthesized a new series of highly functionalized 1,5-ben-zodiazepine derivatives from 3-[(lE)-N-(2-aminophenyl)ethanimidoyl]-4-hydrox-yl-2H-chromen-2-one and pyrazole aldehyde using catalytic amount of trifluoro-acetic acid under microwave irradiation. The major advantages of this process is its shorter reaction time (reduced from 8-10 h to 15-20 min), easy work up procedure, and excellent yield with high purity. 

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