Chromene, 6//-benzo

Fedorova, O.A., Maurel, Fr., Ushakov, E.N., Nazarov, V.B., Gromov, S.P., Chebun kova, A.V., Feofanov, A.V., Alaverdian, I.S., Alfimov, M.V., Barigelletti, Fr. (2003) Synthesis, photochromic behaviour and light-controlled complexation of 3,3-diphenyl-3//-benzo[/]chromenes containing a dimethylamino group or an aza-15-crown-5 ether unit, New J. Chem., 27, 1155-1167. 

Alkylidenecarbenes 124, formed from alkynyliodonium salts 123 and 1-naphthol derivatives, undergo 1,6-C-H insertion at the />m"-position to yield bcnzo[z/ ]chromcncs 125 (Scheme 41) <2001TL6031>. The alkylidenecarbene formed from alkynyliodonium salt 123 and 2-methylnaphthalen-l-ol, can undergo 1,6-C-H insertion at both the /imposition and at the 2-methyl substituent, resulting in a 2 1 mixture of 2,9-dimethylbenzo[r/c ]chromcne and 2-methyl-4//-benzo[ ]chromene (Equation 59) <2001TL6031>. 

Synonym Di-ferf-butyl 3/-/-benzo[/ chromene-2,3-dicarboxylate Source Bahramifar, N. Yamini, Y Ramazani, A. Noshiranzadeh, N. J. Chem. Eng. Data (2003),... 

New acridine-type compounds such as 470 can be synthesized from substituted 3-amino-lH-benzo[/]chromene-2-carbonitrile 469 and cyclohexanone using anhydrous zinc chloride catalyst under reflux (Scheme 103) (08CCL15). Standard reported yields are between 47% and 50%. 

Khafagy, M.M., Abd El-Wahab, A.H.R, Eid, RA., El-Agrody, A.M. 2002. Synthesis of halogen derivatives of benzo[/ ]chromene and benzo[a]anthracene with promising antimicrobial activities. Farmaco 57(9) 715-722. 

A few examples of naphtho[c]chromenes arise from the intramolecular cascade hydroarylation—cycloisomerization reaction of l-(3-phenoxy-l-propynyl)-2-(l-propynyl)benzene derivatives, catalyzed by a PtCl2/PtCl4 system (13EJO260). 3-Trifluoromethylated benzo[ chromenes are readily accessible through the one-pot reaction of a,P-unsaturated trifluoromethyl ketones with 2-naphthols carried out in the presence of DBU and concentrated sulfuric acid (13SC2883). 

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. 

Ammo -(fiiran-2-yl)-5,10-dioxo-5,10-dihydro-4//-benzo[ ]chromene-3-carbonitrile (4eb). Blackish, mp 266-268 °C yield 91%... 

In their report, Khurana and his group [81] also showed that DBU (10mol%) can effectively catalyze the three-component cyclocondensation reaction between aromatic aldehydes, malononitrile or ethyl 2-cyanoacetate, and 2-hydroxynaphthalene-l,4-dione in aqueous medium under reflux to afford 2-amino-4H-benzo[ ] chromenes (10). A series of diversely substituted 2-amino-4-aryl-5,10-dioxo-5,10-dihydro-4ff-benzo[g]chromene-3-carbonitriles and ethyl-2-amino-4-aryl-5,10-dioxo-5,10-dihydro-4H-benzo[j]chromene-3-carboxylates were synthesized using this protocol in excellent yields (Scheme 5). The reactions were claimed to be remarkably clean, and no chromatographic purification was required. 

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. 

SCHEME 12 Synthesis of 2-amino-tetrahydro-4H-chromenes 19 and 2-amino-4H-benzo[/ ]chromenes 20. 

Benzo[b]furan, 2,3-dihydro-2-hydroxymethyl-4//-chromene synthesis from, 3, 764 Benzo[b]furan, 2,3-dihydro-2-isopropenyl-synthesis, 4, 678, 680... 

CB2 Selective Classical Cannabinoids Indoles and Indazoles Resorcinol Derivatives Benzo[c]Chromen-6-one Derivatives... 

Benzo[c]chromen-6-one derivatives, such as AM 1710 (372), were found to be CB2 selective agonists [229]. Although these compounds are structurally similar to the THC derivatives, the dimethyl group on 6-position of the... 

Oxidation of the o-QM complex 13 (formed by treating the phenol complex with (R)-citronellal and pyridine) with CAN resulted in an intramolecular Diels-Alder reaction to form the benzo[c]chromene 15 (Scheme 3.8). 

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>. 

Almost every class of natural phenolic compounds contains examples of substances with a 2,2-dialkylchromene ring, and the number of those that are discovered increases every year. It would be difficult to give an exhaustive list of these compounds. Their chemistry will be discussed here only when it is related to some particular behavior of the benzo-pyran ring. Examples include simple chromenes substituted in the aromatic ring,3,4,35-44 benzodipyrans,3,39 dimers of chromenes,45 naphthopyrans,46,47 quinones,48 flavones,49 flavonols,49 chalcones,49 flavanones,49 isoflavonoids,50 rotenoids,50 pterocarpans,50 couma-rins,17,51-53 3-arvl-4-hydroxycouniarins,50 4-phenylcoumarins,54 chroma-... 

All of the compounds discussed are based on three molecules 2/f-pyran (1), 4//-pyran (2) and the pyrylium cation (3). Names which have been used for the benzologue (4) of 2//-pyran include 2H- 1-benzopyran, benzo-a-pyran, chrom-3-ene and 2//-chromene. A similar situation exists for the corresponding derivative (5) of 4/f-pyran. The unambiguous and simplest name chromene is used in the present work. The benzologue (6) of pyrylium is known both as benzopyrylium and chromylium the former name is preferred here. Higher benzologues are referred to as naphthopyrans, such as 2H-naphtho[ 1,2-6 jpyran (7), but the names xanthene and xanthylium are used for (8) and (9). 

The simple pyrans are rather unstable compounds and of little biological or industrial significance but some of their benzo derivatives are of considerable interest. Many 2H-1-benzopyrans (chromenes) are found in plants, for example evodionol (126), lapachenole (127), lonchocarpin (128), rottlerine (129) and edulan (130). A few of the constituents of marijuana (hashish) belong to this class, for example cannabinol (131). 

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