Coumarins allylation

Cycloaddition of COj with the dimethyl-substituted methylenecyclopropane 75 proceeds smoothly above 100 °C under pressure, yielding the five-membered ring lactone 76. The regiocheraistry of this reaction is different from that of above-mentioned diphenyl-substituted methylenecyclopropanes 66 and 67[61], This allylic lactone 76 is another source of trimethylenemethane when it is treated with Pd(0) catalyst coordinated by dppe in refluxing toluene to generate 77, and its reaction with aldehydes or ketones affords the 3-methylenetetrahy-drofuran derivative 78 as expected for this intermediate. Also, the lactone 76 reacts with a, /3-unsaturated carbonyl compounds. The reaction of coumarin (79) with 76 to give the chroman-2-one derivative 80 is an example[62]. 

C) Preparation of 6-Allyl-7-Hydroxy-4,8-Dimethylcoumarin 7-Allyloxy-4,8-dimethyl-coumarin (195.0 g, 0.84 mol) was heated (oil bath) to 215 4°C (reaction mixture temperature) for 3 hours and was then poured into absolute alcohol (ca 1.5 liters). Activated carbon (Norite) (19.5 g) was added, and the solution was heated to boiling, filtered, and diluted with excess water (ca 12 liters). The product was collected by filtration and partially dried at 70°C for 6 hours. 6-Allyl-7-hydroxy-4,8-dimethylcoumarin was obtained as pale yellow microcrystalline prisms, MP 166° to 168°C, by two recrystallizations from aqueous ethanol of a portion of the partially dried solid. The remaining partially dried solid was used in the next step. 

For preparation of allyl coumarins and dihydrofuranocoumarins by tandem Claisen rearrangement-cyclization the usual procedures required vigorous reaction conditions, workup procedures were tedious, and long reaction times led to low yields. The rearrangement of allyloxycoumarins 48 to dihydrofuranocoumarins 49 has been optimized in good yields in a sealed Teflon containers with BF3-ether in N-methyl-... 

Hydroxyphenol, see Hydroquinone p-Hydroxyphenol, see Hydroquinone 4-Hydroxy-3-(l-phenyl-3-oxobutyl)coumarin, see Warfarin 1 -Hydroxypropane, see 1 -Propanol 3 Hydroxypropene, see Allyl alcohol 3 Hydroxypropionic acid lactone, see p-Propiolactone... 

A recent paper (286) reported the use of a commercially available soluble hybrid support prepared by copolymerization of styrene and allylic alcohol that exhibits a lipophilicity intermediate between that of PS and PEG chains. This support was grafted with a number of functional groups that were reacted with various monomer sets to produce pyrazolo[3,4-Z ]pyridines and coumarins with high yields and purities after precipitation by addition of ethanol or water. Most of the soluble support was recovered after the cleavage and retained the same efficiency in further reaction cycles. Another example is thoroughly described in the next subsection. 

With the necessary carbons present in (49), it can be seen that the scheme of oxidation of the allylic methyl group to the aldehyde level (selenium dioxide), and a reduction of the coumarin with concommitant hydrolysis (zinc/acetic acid), afforded the hydroxy-aldehyde-acid intermediate (57), which expectedly and spontaneously cyclized to the tricyclic lactone (55) under the conditions of the reaction. 

Palladium-based catalysts also bring about cyclopropanations in high-yield. With palladium acetate/CHjNj, styrene , unactivated terminal olefins strained olefins , 1,3-dienesan enamine , as well as a,3-unsaturated carbonyl compounds have been cyclopropanated (Table 1). Contrary to an earlier report, the reaction also works well with cyclohexene if the conditions are chosen appropriately it seems that the notniyst is rapidly deactivated in the presence of this olefin >. Trisubstituted a,p-unsaturated carbonyl compounds were found to be unreactive, and the same is true for the double bonds in diethyl fumarate, maleic anhydride, coumarin and 1,3-dimethyluracil. Whereas the latter two were totally unreactive, [3-1-2] cycloaddition of diazomethane gave pyrazolines in the former two cases. The last entry of Table 1 shows that an allyl alcohol function can still be cyclopropanated, but methylene insertion into the O—H bond is a competing process. 

The N-Trifluoromethanesulfonyl group increases Lewis acidity of (S,S) diazaaluminolidine (85a), which associates with 3-acryloyl-l,3-oxazolidine-2-one conformationally tightly so as to control the preferred one-side access of the diene in the transition state 86 of the reaction of 87 with 88, as shown in Scheme 5.23 [8]. The same catalysts (85a-c) have been employed for asymmetric radical allylation on the quaternary carbon of coumarin derivatives [9]. Highly trifluoromethylated diols (90 and 91) have... 

A method for microwave-assisted transesterifications has been published [74]. The microwave-mediated derivatization of poly(styrene-co-allyl alcohol) was investigated as key step in the polymer-assisted synthesis of heterocycles. The procedure was applied to several j8-ketoesters and multigram quantities of products were obtained when neat mixtures of the reagents in open vessels were exposed to micro-wave irradiation in a domestic microwave oven. The soluble supports obtained were used for preparation of a variety of bicyclic heterocycles, for example pyrazo-lopyridinediones or coumarins. 

COUMARILIC ACID, 24, 33 Coumarin, 24, 33 Coumarin dibromide, 24, 33 Coumarin, 4-methyl-, 24, 69 Coupling, of allyl chloride, 27, 7 of aryl residues, 20, 45 Crab shells, 26, 36 Creatinine, 22, 90 /i-Cresol, 2-bromo-, 23,11 Crotonaldehyde, 24, 92 27, 66 Crotonic acid, SO, 101 24, 98 26, 55 Crotonio acid, /3-anilino-, ethyl ESTER, 29, 42 Cupric acetate, 28, 45 Cupric carbonate, basic, 24, 64 Cupro-cupri sulfite, 28, 53 Cuprous bromide, 24, 22, 23 Cuprous chloride, 28, 46 Cuprous cyanide, 21, 89 24, 14, 97 28, 34... 

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