Benzo chromen-6-ones synthesis

S. Samai, G. C. Nandi, M. S. Singh, Tetrahedron 2012, 68, 1247-1252. Highly convergent one-pot four-component regio-selective synthesis of 4H-benzo[/]chromenes via annulation of P-oxodithioesters. 

J.M. Khurana, B. Nand, P. Saluja, DBU a highly efficient catalyst for one-pot synthesis of substituted 3,4-dihydropyrano[3,2-c]chromenes, dihydropyrano[4,3-fc]pyranes, 2-amino-4H-benzo[/t]chromenes and 2-amino-4H-benzo[ ]chromenes in aqueous medium. Tetrahedron 66 (2010) 5637-5641. 

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. 

Hydroxymethyl-4,8-dimethylfuro[2,3-/z]chromen-2-one was realized in an efficient manner via a Claisen rearrangement of 4-(hydroxybut-2-ynyloxy)-4-methylchromen-2-one as depicted in the following scheme. Other examples with substitution of hydroxyl and with other substituents, such as chloro, amino, acetoxy were also reported <06JHC763>. A new approach for the synthesis of oxygenated benzo[fe]furans was developed via epoxidation and cyclization of 2 -hydroxystilbene <06T4214>. 

As demonstrated below, a Lewis acid-mediated reaction was utilized in the synthesis of dihydro[b furan-based chromen-2-one derivatives from l-cyclopropyl-2-arylethanones and allenic esters <070L4017>. The TiCh-catalyzed anti-Markovnikov hydration of alkynes, followed by a copper-catalyzed O-arylation was applied to the synthesis of 2-substituted benzo[6]furan <07JOC6149>. In addition, benzo[6]furan-based heterocycles could be made from chloromethylcoumarins <07SL1951>, substituted cyclopropanes <07AGE1726>, as well as benzyne and styrene oxide <07SL1308>. On the other hand, DBU-mediated dehydroiodination of 2-iodomethyl-2,3-dihydrobenzo[6]furans was also useful in the synthesis of 2-methylbenzo[Z>]furans <07TL6628>. 

A potentially useful one-pot procedure for the conversion of suitable aryl thiols to benzo[6]thiophenes or napththo[2,l-6]thiophenes in the presence of silica supported acidic and basic reagents has been devised, as exemplified by the synthesis of the system 9 from 2-naphthalenethiol 10 <05SL2739>. A stepwise variant of the same theme has been employed in a synthesis of 6-bromo-l,2,3,4-tetrahydrodibenzothiophene, a partner for a Suzuki coupling leading to a chromene-4-one containing inhibitor of DNA-dependent protein kinase <05JMC7829>. 

The intramolecular asymmetric Heck reaction has featured in the synthesis of complex heterocyclic compounds. Bidentate ligands, such as diphosphines (especially BINAP) and phosphine—oxazolines, have been used as a chiral ligand of the asymmetric Heck reaction. Imbos et al. demonstrated that the mono-dentate phosphoramidite 513 was an effective ligand for the asymmetric Heck reaction of the prochiral cyclohexadienone 511 (Scheme 153).227 The reaction of 511 in the presence of catalytic amounts of Pd-(OAc)2 and the chiral phosphoramidite 513 gave the 4a-methoxy-4a//-benzo[c]chromen-2(6E/)-one 512 in 71% yield with 96% ee. By contrast, the reaction of... 

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... 

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... 

Singh and coworkers have reported the synthesis of various 3-substi-tuted-2H-chromen-2-ones 41 and benzo[ 2H-chromen-2-ones 42 from a condensation of 2-hydroxyarylaldehydes and a-oxoketene dithioacetals in the presence of InCl3 under solventless system (Scheme 31) (12T8683). 

A variety of substituted 2-amino -aryl-4H-benzo[/f]chromene derivatives were synthesized from one-pot multicomponent reaction of aromatic aldehydes, malononitrile, and 1-naphthol in aqueous media. In 2004, Maggi and coworkers [79] explored the use of basic alumina as a useful heterogeneous and reusable catalyst for the synthesis of 2-amino-4H-chromenes (8) from the reaction of these substrates in water under reflux condition (Scheme 3). Only a-naphthol was found to be capable of xmdergoing this reaction as an activated phenol although, the easy purification of products simply by crystallization, the use of water as solvent, and of y-alumina as a heterogeneous and reusable catalyst suggest good prospect for the industrial applicability of this process. A simple, clean, and environmentally... 

M. Khoobi, L. Ma mani, F. Rezazadeh, Z. Zareie, A. Foroumadi, A. Ramazani, A. Shafiee, One-pot synthesis of 4H-benzo[b]pyrans and dihydropyrano[c]chromenes using inorganic-organic hybrid magnetic nanocatalyst in water, J. Mol. Catal. A Chem. 359 (2012) 74-80. 

Preparation of a s-cannabidiol by Minuti [72] was effected by the synthesis of 6a-cyano-tetrahydro-6H-benzo[c] chromen-6-ones 198 based on the Diels-Alder cycloaddition under high pressure of 3-cyano-coumarins 196 and 1,3-butadienes 197 (Scheme 48). Cycloadditions carried out at the atmospheric pressure gave the same adducts in significantly lower yields, but at the high temperature (150 °C). The cycloadduct 198a was subsequently converted to cis-cannabidiol in two reaction steps. 

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

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