Synthesis coumarins

The reaction of o-iodophenol, norbornadiene and CO proceeds via alkene and CO insertions to afford the lactone 562, which is converted into coumarin (563) by the retro-Diels-Alder reaction. In this coumarin synthesis, norbona-diene behaves as a masked acetylene[4)3],... 

Coumarin synthesis trom phenols and ethyl acetoaceiaie. 

Fig. 2 Representative traditional methods for coumarins synthesis, (a) Perkin synthesis (b) Pechmann-type condensation (c) Knoevenagel-type condensation...

In the second investigation [34], involving a coumarin synthesis by Knoevenagel condensation, supported by rate constant measurements and activation energy calculations, it was found that the effect of MW was more important when the reaction was conducted in xylene - it was noticeably reduced in ethanol (Eq. (5) and Tab. 3.3). 

A three-component coumarin synthesis involves the Pd-catalysed coupling of o-iodophenols with alkynes and subsequent insertion of carbon monoxide. With internal alkynes, pyridine is the crucial base for successful annulation the regioselectivity with unsymmetrically substituted alkynes is only moderate (Scheme 43) . 

Coumarin, soluble dyes, 7 373t Coumarin synthesis, microwaves in,... 

The most important FBAs in the coumarin series are the 7-amino-3-phenylcoumarins which are prepared via the Pechmann coumarin synthesis. For example, m-aminophenol may be condensed with ethyl 3-hydroxy-2-phenylacrylate in the presence of a Lewis acid in nitrobenzene (Scheme 13). 

A further illustration of the reaction of carbanionic species with o-hydroxybenzaldehydes is provided by the use of phosphorus ylides in coumarin synthesis. Thus, ethoxycarbonyl-methylenetriphenylphosphorane affords simple coumarins via the ester (380 R = H), whilst with o-hydroxyacetophenone a 4-methylcoumarin results (381 R = Me) (77S464), and 4-methylsulfinylmethylcoumarin (381 R = CH2SOMe) is obtained from o-hydroxy-a>-methylsulfinylacetophenone (Scheme 120) (72JHC175). 

Application of the Perkin cinnamic acid synthesis to salicylaldehydes provides a coumarin synthesis of some renown. The reaction itself has been reviewed <42OR(l)2l0) and some discussion of its value in coumarin synthesis is contained in other reviews (37CB(A)83, 45CRV(36)l). 

Coumarin, 7-diethylamino-4-methyl-fluorescence, 3, 879 Coumarin, dihydro-chroman synthesis from, 3, 785 4H-chromene synthesis from, 3, 765 coumarin synthesis from, 3, 810 mass spectra, 2, 23 synthesis, 3, 848 Coumarin, 3,4-dihydro-4,4-disubstituted synthesis, 3, 754... 

The Pechmann Condensation ( or Coumarin Synthesis) allows the synthesis of coumarins by reaction of phenols with p-keto esters. 

Coumarins are an important family of fragrance chemicals with herbaceous, haylike odors. The conventional methods for coumarin synthesis require drastic conditions. For example, 4-methyl-7-hydroxycoumarin 39 (Eq. 15.4.1) is prepared via the Pechmann reaction by stirring a mixture of resorcinol 37 and ethyl acetoacetate 38 in H2SO4 for 12-14 h (63). 

The formation of courmarin derivatives using phenols or phenolic analogues is an example of the von Peckman-Duisberg coumarin synthesis reaction and is reviewed (3). 

Deshpande, P. R Baker, D. C. A simple approach to the synthesis of the chiral substituted chroman ring of calophyllum coumarins. Synthesis, 1995, 630-632. 

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