palladium-catalyzed carbonylation of coumarins involving two C–C bond formations has been developed. The C–H bond oxidative functionalization proceeds through aroylation with insertion of carbon monoxide to give arylcoumarin ketones. The reaction conditions, employing ambient pressures of CO gas as C1 feedstock, dramatically improve the generality of the carbonylation of arylhalides. A facile and efficient
Transition metal-free cross-dehydrogenative coupling acylation of coumarins by the K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>/Aliquat 336 catalytic system: a versatile strategy towards 4-aroylcoumarin derivatives
A new and efficient transition metal-free oxidative cross-dehydrogenative coupling (CDC) reaction is described for the preparation of 4-aroylcoumarin derivatives. In this protocol aldehydes have been used as acylating agents for acylation of 3-substituted coumarins throughC(sp2)–C(sp2) bondformation using the K2S2O8/Aliquat 336 system as an inexpensive and environmentally friendly reagent. The reactions
描述了一种新型的高效无过渡金属的氧化性交叉脱氢偶联(CDC)反应,用于制备4-芳酰基香豆素衍生物。在该方案中,醛已被用作酰化剂,使用K 2 S 2 O 8 / Aliquat 336系统作为廉价且环保的试剂,通过C(sp 2)–C(sp 2)键形成三取代的香豆素。。反应在乙腈中于80°C进行2-3小时,以高收率得到相应的4-芳酰基香豆素衍生物。
Transformation of a hydroxyl into an acyl group on α-pyrone ring: a novel route to 3,4-diacylcoumarins
作者:Antigoni Kotali、Despina A. Nasiopoulou、Philip A. Harris、Madeleine Helliwell、John A. Joule
DOI:10.1016/j.tet.2011.10.086
日期:2012.1
The transformation of a hydroxyl into an acyl group, a transformation which has been extensively investigated on the benzene nucleus of several substrates, is now applied successfully for the first time to a heterocyclic ring and specifically to the pyrone ring of coumarin to yield novel 3,4-diacylcoumarins in good yields. The reaction involves formation of a new C–C bond.