Solvent-free, efficient, and mild 2-pyrone synthesis by the cycloaddition of alkynes with CO2 has been achieved under compressed CO2 with a Ni(cod)2/P(C4H9)3 or Ni(cod)2/P(C8H17)3 catalyst; both high yields (up to 98%) and selectivities (up to 99%) are attained. One attractive aspect of these catalysts is their high efficiency at low CO2 pressures (4 MPa). The applicability of this reaction to a broad range of alkyne substrates and the ease of handling the phosphine ligands are additional merits of the present new catalytic systems in comparison to the previously reported Ni(cod)2/P(CH3)3 catalyst in supercritical CO2.
在压缩
二氧化碳环境下,通过
炔烃与
二氧化碳的环加成反应,在Ni(cod)2/P(
C4H9)3或Ni(cod)2/P(
C8H17)3催化剂的作用下,实现了无溶剂、高效且温和的2-
吡喃合成;同时获得了高收率(高达98%)和高选择性(高达99%)。这些催化剂的一个吸引人的方面是它们在低
二氧化碳压力(4 MPa)下的高效率。与之前报道的超临界
二氧化碳中的Ni(cod)2/P(
CH3)3催化剂相比,这种反应对
炔烃底物的广泛适用性以及
膦配体的易处理性是当前新催化系统的额外优点。