Studies On The Palladium-catalyzed Transformation Reactions Of CO2and Co, And The C-n Coupling Reactions

CO2and CO are important C1building blocks in organic synthesis. The palladium-catalyzed transformation reactions of them were paid more and more attention by chemists. Various unsaturated carbonyl compounds, such as unsaturated esters, aldehydes, ketones, could be prepared through carboxylation or carbonylation of allyl halides, benzyl halides,1,3-conjugate dienes, allenes via allyl palladium intermediates.1,3-Butadiene can be used for palladium-catalyzed telomerization reaction with CO2to produce unsaturated ester (E)-3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (δ-lactone1) selectively. This is an efficient way for comprehensive utilization of1,3-butadiene and CO2. However, the reported ligands for selective synthesis of δ-lactone1all suffered from air-sensitivity, which hinder their applications in laboratory or industry. In addition, under CO atmosphere, a series of aryl acetyl compounds could be synthesized by palladium-catalyzed carbonylative coupling. In comparison with literature methods, the new method has below advantages:use of simple substrates, mild reaction conditions, and short-step synthesis.In the present study, a series of P,N-bidentate ligands L1-L7based on the air-stable triphenylphosphine (PPh3) with ortho-substituted cyclic secondary amino groups on benzene rings were synthesized for the selective synthesis of δ-lactone1. In the telomerization reactions of CO2with1,3-butadiene, catalytic system4-(2-(diphenylphosphino)phenyl)-morpholine L2/Pd2(dba)3gave the best result for selective synthesis of δ-lactone1. The target product δ-lactone1was obtained in60%yield with79%selectivity under the optimized reaction conditions. In addition, the chelating coordination mode of the P,N-bidentate ligands to the palladium center was confirmed by determining the X-ray structures of the Pd(II) complexes C1and C2derived from ligands1-(2-(diphenylphosphino)phenyl)piperidine (L1) and L2.In this work, a series of β,γ-unsaturated ketones4were prepared from carbonylative coupling of ortho-bromobenzyl bromides3and allyltributylstannane with73%-90%yields. Under basic conditions,β,γ-unsaturated ketones4could be isomerized to give α,β-unsaturated ketones5quantitatively. A series of2-naphthol derivatives6were formed up to89%yield via intramolecular Heck conditions of5. Among the newly formed P,N-ligands of L1-L7, tris(2-morpholinophenyl)phosphine (L7) is steric bulky, electronic richness, which was demonstrated that is a suitable ligand for palladium-catalyzed C-N coupling reaction. When Pd2(dba)3/L7was used as a catalyst system, aryl bromides and secondary amines could be coupled effectively to give various aryl amines in84%-95%yields. The air-stable ligand L7can be prepared easily.