4-Hydroxy coumarine

In order to study any chemoselectivity influences of microwave irradiation on the domino Knoevenagel/hetero-Diels-Alder process (the so-called Tietze reaction), Raghunathan and coworkers [31a] investigated the transformation of 4-hydroxy coumarins (10-85) with benzaldehydes 10-86 in EtOH to afford pyrano[2,3-c]cou-marin 10-87 and pyrano[2,3-b]chromone derivatives 10-88. Normal heating of 10-85a and 10-86a at reflux for 4h gave a 68 32 mixture of 10-87a and 10-88 in 57% yield, whereas under microwave irradiation a 97 7 mixture in 82% yield was obtained. Similar results were found using the benzo-annulated substrates 10-85b and 10-86b. 

Synonyms 3 -(a-Acetonylbenzyl)-4,hydroxy-coumarin coumadin compound 42... 

The transformation could also be performed using a chiral enantiopure enol ether as dienophile. The best results were achieved with the isopropenyl ether 182b derived from cheap and commercially available (—)-(lR,2S,5R)-menthol. The cycloadduct was obtained with an endo/exo-selectivity of 4.1 1 and an induced dia-stereoselectivity of 88 12. Treatment of 178b with trifluoroacetic acid/water 19 1 provided (S)-warfarin 175 in an overall yield of 61% referred to 4-hydroxy coumarin 55 and an enantiomeric excess of 76% (HPLC), which could be increased to 95% ee by recrystallization using the purified endo-product 178b as substrate for the hydrolysis. In the same manner (S)-coumachlor 176 and (S)-acenocoumarol 177 were obtained with 56% overall yield and 93% ee and 59% overall yield and 95% ee, respectively. 

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). 

A synthetic route to l,4-diazepin-5-ones such as 227 has been crafted by the reaction of 4-hydroxy coumarin 193 with 1,2-diamines under heating (Scheme 26) <1997JHC1821>. A variety of diamines were examined in this study, and obvious issues of regiochemistry arose with the use of unsymmetrical 1,2-diamines. 

The intramolecular lactonization of 3-(2-acetoxyphenyl)-3-hydroxyacrylic acid derivatives 663 to afford 4-hydroxy-coumarins can be achieved under either acidic or basic conditions in good yield (Equation 269) <2004S1775>. 

A tellurium-triggered cyclization of methyl 2-(2-bromoacetoxy)benzoates 671 affords 4-hydroxy coumarins in good yield (Scheme 160) <2005JOC4682>. Similarly, the tellurium-triggered cyclization of 2-formyl and 2-acetyl-phenyl 2-bromoacetates 672 provides coumarins (Equation 271) <2005JOC4682>. 

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>. 

Hydroxy Coumarine a Versatile Reagent for the Synthesis of Heterocyclic and Vanillin Ether Coumarins with Biological Activities... 

Abstract We report here the synthesis of newly coumarinic derivatives by using 4-hydroxy coumarine as starting material. These newly compounds were screened in vitro for their antimicrobial and antifungal activities. The structures of the synthesized compounds were proved by IR, H NMR, 13 C NMR and mass-spectral. 

Shah VR, Bose JL, Shah RC (1960) New synthesis of 4-hydroxy coumarins. J Org Chem 25 677... 

Haywood, D.J., Hunt, R.G., Potter, C.J., and Reid, S.T. (1977) Photochemical transformations. Part 10. Photocydo-addition reactions of 4-hydroxy-coumarin with cycloalkenes. Journal... 

Kappe et al.3S1 have prepared 3,6-bis(2-hydroxyphenyl)-2,5-dihydropyrazine (181) by alkaline treatment of 3-amino-4-hydroxy-coumarin (180). Compound 181 is conveniently dehydrogenated over... 

A more unusual starting material is 3 carbethoxy 4 hydroxy coumarin (obtained by reaction between salycylaldehyde and malonic acid) which undergoes decarboxylation when reacting with benzalacetone. 

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