Department of Pharmaceutical Sciences, Yokohama University of Pharmacy 601 Matano-cho, Totsuka-ku, Yokohama, 245-0066, Japan.
Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan.
Chemistry. 2023 Jan 27;29(6):e202203068. doi: 10.1002/chem.202203068. Epub 2022 Dec 20.
Palladium(0)/monophosphine complexes catalyze anti-selective alkylative, arylative, and alkynylative cyclizations of alkynyl electrophiles with organometallic reagents. The remarkable anti-selectivity results from novel oxidative addition, that is, the nucleophilic attack of electron-rich palladium(0) on the electrophile across the alkyne followed by transmetalation and reductive elimination ("anti-Wacker"-type cyclization). With regard to 5-alkynals, triphenylphosphine (PPh )-ligated palladium(0) catalyzes the cyclization of terminal alkynes and conjugated alkenyl- or alkynyl-substituted ones to afford 2-cyclohexen-1-ol and 2-alkylidene-cyclopentanol derivatives, respectively. For 6-alkyl- or 6-aryl-5-alkynals, the cyclization does not proceed with the palladium/PPh catalyst; however, it does proceed with palladium/tricyclohexylphosphine (PCy ), to yield the former products predominantly. Remarkably, the latter catalyst completely switches the regioselectivity in the cyclization of the conjugated diyne-aldehydes. Notably, palladium/PPh -catalyzed cyclizations also proceed with other organometallics or even without them.
钯(0)/单膦配合物催化炔烃亲电试剂与有机金属试剂的反选择性烷基化、芳基化和炔基化环化反应。显著的反选择性源于新型氧化加成，即富电子钯(0)对亲电试剂的亲核攻击跨越炔烃，然后进行转金属化和还原消除（“反-Wacker”-型环化）。对于 5-炔醛，三苯基膦 (PPh )-配位钯(0)催化末端炔烃和共轭烯基或炔基取代的炔烃的环化反应，分别得到 2-环己烯-1-醇和 2-亚烷基环戊醇衍生物。对于 6-烷基-或 6-芳基-5-炔醛，钯/PPh 催化剂的环化反应不能进行；然而，钯/三环己基膦 (PCy )催化剂可以进行，主要得到前一种产物。值得注意的是，后一种催化剂完全改变了共轭二炔醛环化反应的区域选择性。值得注意的是，钯/PPh -催化的环化反应也可以与其他有机金属试剂或甚至没有它们进行。
