3.4- Dihydrocoumarins, synthesis

Propionic acid, 2-bromo-3-(3-indolyl)-methyl ester rearrangement, 4, 279 Propionic acid, 3-(3,4-dimethyoxyphenyl)-dihydrocoumarin synthesis from, 3, 848 Propionic acid, indolyl-synthesis, 4, 232 Propionic acid, 3-(l-indolyl)-sodium salt pyrolysis, 4, 202 Propionic acid, 3-(3-indolyl)-intramolecular acylation, 4, 220, 221 Propionic acid, 3-phenoxy-chroman-4-one synthesis from, 3, 855 Propionic acid, 3-(3-phenylisoxazoI-5-yl)-bromination, 6, 25... 

A similar intramolecular alkylation of arene-ene substrates is catalyzed by RuGl3/AgOTf, providing good to excellent yields of cyclization products (chromanes, tetralins, terpenoids, and dihydrocoumarins).25 This method is applied to the synthesis of tricyclic terpenoids, which are formed in nearly quantitative yields with high stereoselectivities (trans cis various between 99 1 and 99 2), as shown in Equation (24). 

Catalytic asymmetric hydrogenation of 4-aryl coumarins provides a key step in the synthesis of a class of endothelin receptor antagonists <1999TL3293>. Raney Nickel can be used to achieve the chemoselective hydrogenation of coumarins to dihydrocoumarins in excellent yield <1999SL1663>. 

The outcome of the reaction of phenols with 5-alkylidene Meldrum s acids 25 catalysed by Yb triflate in the synthesis of O-heterocycles is dependent upon the nature of the alkylidene unit. Two distinct Friedel-Crafts sequences are apparent in this mild and simple route to coumarins and dihydrocoumarins and to chromones and chroman-4-ones (i) C-alkylation - (9-acylation and (ii) C-acylation - (9-alkylation <06JOC409>. 

Oxidation of i-(alkoxyaryl)proplonlc acids. This reaction of TTFA can be used for synthesis of dihydrocoumarins and spirohexadienone lactones and of p-benzoquinones. An example of both sequences is formulated in equation (I). ... 

Scheme 17 Rhodium-catalyzed asymmetric synthesis of dihydrocoumarins...

Dihydrocoumarins and Dihydroisocoumarins. - The potential of thalHum compounds in organic synthesis continues to be developed in a variety of reactions. One of these was the synthesis of dihydrocoumarins by oxidative cyclization of 3-arylpropionic acids, e.g. (177), by thallium(in) trifluoro-acetate-trifluoracetic acid (TTFA). The coumarin was accompanied by methyl 3-(2-hydroxyphenyl)propionate (178), which was formed by ring-... 

Viaje, A., T.J. Siege, M. Wigler, and LB. Weinstein Effects of anti-inflammatory agents in mouse skin tumor promotion, epidermal DNA synthesis, phorbol ester-induced cellular proliferation, and production of plasminogen activator Cancer Res. 37 (1977) 1530-1536. Viart, P. Aromatization of tobacco. Determination of coumarin, dihydrocoumarin, ethylvanUhn and vanillin in tobacco and its smoke Aim. Dir. Emdes Equipement, SETTA 8(Sect. 1) (1970) 151-152. 

The name coumarone, which was previously used for benzo[6]furan, originates from this synthesis. The reaction of the intermediate 3,4-dibromO 3,4-dihydrocoumarin with KOH leading to benzofuran is known as Perkin rearrangement. 

In the synthesis of coumarins by the von Pechmann reaction, a spiro-compound (251) was simultaneously formed from 4-chloro-2-methylphenol (and from 2,3,5-trimethylphenol). A possible mechanism for this reaction involves the formation of the lactone (252), which reacts with another molecule of the phenol. The condensation of the dicyano-ester (253) [obtained from malononitrile and ethyl cyanoacetate] with substituted o-hydroxybenzaldehydes yields substituted coumarinimines, e.g. (254).A series of 4,6,7-substituted coumarins have been prepared and assessed for their suitability in fluorescence labelling of polymers. Esters of the type PhCH CRCOaAr react with AICI3 to give coumarins, which are probably formed via dihydrocoumarins (255) by dearylation. ... 

KIO is also effective in the synthesis of coumarins from phloroglucinol and 3-arylpropynoyl chlorides and of 3,4-dihydrocoumarins using cinnamoyl chlorides. At high... 

Ye and his co-workers reported an enantioselective synthesis of 3,3,4-trisubstituted 3,4-dihydrocoumarins 150 via iV-heterocyclic carbene-catalyzed cycloaddition of ketenes 148 and o-quinone methides 147, Scheme 3.48 [64], Noteworthy, it was found that the additive methanol was crucial for the high yields and enantioselectivities. However, the rationalization for the use of the additive methanol remains unclear. 

Scheme 3.48 Organocatalytic enantioselective synthesis of 3,3 4-trisubstituted 3,4-dihydrocoumarins...

Environmentally benign synthesis routes for umbelliferone (I), 7-hydroxy-4-methylcoumarin (II), 3,4-dihydrocoumarin (III), and tricyclic coumarin (IV) (Figure 10.2) were developed using zeolite-H-p or Amberlyst-15 as solid catalysts. This resulted in the minimization of harmful mineral acid wastes. The reactions of resorcinol with acrylic acid, propynoic acid, and ethyl acetoacetate were investigated in toluene and p-chlorotoluene under reflux conditions to obtain coumarins in 60%-80% yield (Hoefnagel et al. 1995 Gunnewegh et al. 1995). 

Rezayan, P. Azerang, S. Sardari, A. Sarvary, Chem. Biol. Drug Des. 2012, 80,929-936. Synthesis and biological evaluation of coumarin derivatives as inhibitors of mycobacterium bovis (BCG), (c) A. Shaabani, A. Sarvary, E. Soleimani, A. H. Rezayan, M. Heidary, Mo/. Divers. 2008,12,197-202. A novel method for the synthesis of snbstitnted 3,4-dihydro-coumarin derivatives via isocyanide-based three-component reaction, (d) A. Shaabani, E. Soleimani, A. H. Rezayan, A. Sarvary, H. R. Khavasi, Org. Lett. 2008, 10, 2581-2584. Novel isocyanide-based four-component reaction a facile synthesis of fuUy substituted 3,4-dihydrocoumarin derivatives. 

Shaabani, A., Soleimani, E., Rezayan, A. H., Sarvary, A., and Khavasi, H. R. (2008). Novel Isocyanide-based four-component reaction A facile synthesis of fully substituted 3,4-dihydrocoumarin derivatives. Org. Lett., 10, 2581-2584. 

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