Synthesis of Benzopyrans with Polymer-Supported Palladacycles

Significance

Polystyrene-divinylbenzene (PS-DVB)-supported palladacycles 1 were prepared, and benzopyrans were received following the reaction of palladacycles 1 with alkynes or allenes. The polymer-supported palladacycles 1a-c were prepared by treating the TMEDA palladium complex with PS-DVB-supported triphenylphosphines with different phosphorus loading levels (1a: 0.9 mmol/g, 1b: 1.4 mmol/g, 1c: 3.0 mmol/g) in the Pd:P molar ratios of 1:1.7-6.0 (eq. 1). The PS-DVB-supported palladacycle 1b with the phosphorus loading of 1.4 mmol/g in a Pd:P ratio of 1:1.7 showed the highest reactivity. The reaction of the optimum palladacycle 1b with arylpropio­lates gave 4-aryl-2H-1-benzopyrans in 70-94% yields. 4-Alkylidene-3,4-dihydro-2H-1-benzopy­rans were also obtained by reaction of pallada­cycle 1b with 1,2-nonadiene and 5-ethyl-1,2-nonadiene in 90% and 76% yields, respectively.