Coumarins 4-hydroxy-3-aryl

Coumarin, 7-amino-7-(diethylamino)-, I, 333 Coumarin, 7-amino-4-methyl-fluorescence spectra, 3, 601 Coumarin, 7-amino-3-phenyl-brightening agents, I, 339 Coumarin, 4-aryl-occurrence, 3, 677 synthesis, 3, 810 Coumarin, 3-arylazo-4-hydroxy-structure, 3, 643 Coumarin, 3-bromo-reactions... 

Hydroxycoumarins can be converted into 4-arylcoumarins via the Pd-catalysed coupling of 4-stannylcoumarins with aryl iodides (95SC2883), whilst the three component reaction of 4-hydroxy-coumarins, triethyl orthoformate and hydrazines yields A-derivatives of 3-methylenechroman-2,4-diones (95M579). 

In the presence of a ruthenium catalyst, 3-diazochroman-2,4-dione 716 undergoes insertion into the O-H bond of alcohols to yield 3-alkyloxy-4-hydroxycoumarins 717 (Equation 285) <2002TL3637>. In the presence of a rhodium catalyst, 3-diazochroman-2,4-dione 716 can undergo insertion into the C-H bond of arenes to yield 3-aryl-4-hydroxy-coumarins (Equation 286) <2005SL927>. In the presence of [Rh(OAc)2]2, 3-diazochroman-2,4-dione 716 can react with acyl or benzyl halides to afford to 3-halo-4-substituted coumarins (Equation 287) <2003T9333> and also with terminal alkynes to give a mixture of 477-furo[3,2-f]chromen-4-ones and 4/7-furo[2,3-3]chromen-4-ones (Equation 288) <2001S735>. 

Another type of reaction of 4-hydroxycoumarin is condensation with aryl-alkylcarbinols. Thus, condensation of 4-hydroxycoumarin with a-hydroxytetraline (24) in acetic acid solution yields 3-(l,2,3,4-tetrahydronaphthyl)-4-hydroxy-coumarin (coumatetralyl, 25) (Hermann and Hombrecher, 1962). 

A palladium-catalyzed Suzuki coupling reaction of phenyliodonium zwitterions 56 with aryl boronic acids has been developed. The unique characteristics of the mild reaction conditions and convenient synthetic accessibility of phenyliodonium zwitterions make this method a valuable tool for generating diversified 3-aryl-4-hydroxy-coumarins (Equation 99) [143],... 

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