We have developed a highly efficient reaction for catalytic asymmetric addition of malonates to dihydroisoquinolines using chiral Pd(II) complexes. In the reactions, substrates with various substitution patterns were available, and the reactions were complete within several hours (<3 h in most cases) under mild reaction conditions, affording various optically active C1-substituted tetrahydroisoquinoline derivatives (up to 98% yield, up to 97% ee). Furthermore, slow addition of DDQ allowed the in situ generation of the reactive intermediate from the corresponding N-Boc-protected amine, and dehydrogenative addition reaction was successfully demonstrated.

Detailed mechanistic studies on our recently reported asymmetric addition reactions of malonates to dihydroisoquinolines (DHIQs) catalyzed by chiral Pd(II) complexes were carried out. It was found that an N,O-acetal was generated in situ by the reaction of DHIQ with (Boc)2O, and cooperative action of the Pd(II) complex as an acid-base catalyst allowed the formation of a chiral Pd enolate and a reactive iminium ion via alpha-fragmentation. The iminium ion was also accessible via oxidation with DDQ as an oxidant, and a catalytic asymmetric oxidative Mannich-type reaction was achieved with tetrahydroisoquinolines (THIQs) as starting materials. This oxidation protocol was applicable to N-acryloyl-protected THIQs, allowing the efficient synthesis of optically active tetrahydrobenzo[a]quinolizidine derivatives via intramolecular Michael reaction.

The dirhodium-tetracarbonyl complex with the PNNP ligand, [Rh 2 (PNNP)(CO) 4 ]BF 4 , 1‚BF 4 [PNNP ) 3,5-bis(diphenylphosphinomethyl)pyrazolato], serves as a precursor for the active species [Rh 2 (PNNP)(CO) 2 ] + , A, with cis-divacant coordination sites, which can accommodate a donor species with up to four donor electrons. Interaction of 1‚BF 4 with LiCtC-R, Li-CHdCH 2 , PPN[M(CO) n ], CN-Cy, SMe 2 , and Et-CtC-Et leads to the formation of the corresponding dinuclear adducts [(X)Rh 2 (PNNP)(CO) 2 ] n+ (BF 4 ) n [X/n ) µ-η 1 :η 2 -CtC-R/0 (2), µ-η 1 :η 2 -CHdCH 2 /0 (3), µ-Co(CO) 4 /0 (4a), µ-Mn(CO) 5 /0 (4b), (η 1 -CtN-Cy) 2 /1 (5‚BF 4 ), µ-η 1 :η 1 -SMe 2 /1 (6‚BF 4 ), µ-η 2 :η 2 -Et-CtC-Et/1 (7‚BF 4 )], respectively. Selective replacement of the inner CO ligands trans to the P atoms is verified by spectroscopic and crystallographic characterizations of the adducts. The µ-acetylide (2) and µ-vinyl complexes (3) show dynamic behavior via the conventional windshield wiper motion of the unsaturated hydrocarbyl ligand. Systematic structural analysis of a series of the µ-acetylide complexes 2 (R ) H, SiMe 3 , n-Bu, Ph, p-tol) reveals three typical conformations for the Rh 2 (PNNP)(CO) 2 backbone: C s -(type I), C 2 -(type II), and C 2v -symmetrical ones (type III). On the other hand, interaction of 1‚BF 4 with 1-alkyne, hydrosilanes, and hydroxo anion produces tetranuclear adducts resulting from 1 (donor):2 [Rh 2 (PNNP)(CO) 2 ] coupling reactions. The µ 4 -η 1 (C R ):η 2 (C R tC )-acetylide complexes, [(µ 4 -CtC-R)Rh 4 (PNNP) 2 (CO) 4 ]BF 4 , 8‚BF 4 , consisting of an acyclic, folded Z-shaped Rh 4 linkage are fluxional via a combination of windshield wiper-like motions between the wingtip Rh centers and between the wingtip and hinge Rh centers, which involve reversible M-M bond scission and recombination processes. The ethynyl complex 8a‚BF 4 (R ) H) is readily deprotonated by the action of a base to give the µ 4 -dicarbide complex (µ-η 1 :η 1 :η 2 :η 2 -CtC)Rh 4 (PNNP)(CO) 4 , 9, via cleavage of three Rh-Rh bonds, and this process is reversed upon protonation of 9 with HBF 4 . The reaction of 1‚BF 4 with hydrosilanes and hydroxo anion furnishes the isostructural tetranuclear complexes [(µ 4 -X)Rh 4 (PNNP)(CO) 4 ] n+ -(BF 4 ) n [X/n ) H/1 (10‚BF 4 ), O/0 (11)], in which the four Rh atoms arranged in a tetrahedral array are connected by the µ 4 -bridging ligand (X), as characterized by X-ray crystallography. The tetranuclear structures are retained mainly by Rh-X interactions even in the case of the electron-deficient hydride complex 10‚BF 4 with 58 valence electrons (cf. 64e for a coordinatively saturated species), where the filled, spherically distributed 1s orbital of the hydride ligand interacts with the four Rh centers arranged in a tetrahedral array. Depending on the size of the bridging ligand X, the structure of the tetranuclear complexes varies from the encapsulated structure (10‚BF 4 and 11) to the one with a folded Z-shaped metal linkage (8‚BF 4 ). The present study reveals (i) the high reactivity (electr...

Pairs of isomeric heterodinuclear complexes, [(cod)Ir(mu-PNNN)M(L)]BF4 and [(L)M(mu-PNNN)Ir(cod)]BF4, with switched metal arrangements are prepared in a specific manner by simply changing the addition order of the reagents.

The ligands 2,6-bis{[(pyrid-2-ylmethyl)amino]methyl}-pyridine with an N 5 pattern and (6-{[(pyrid-2-ylmethyl)amino]methyl}pyrid-2-yl)methanol with an N 3 O pattern were synthesized. Zn II complexes of the two ligands could be obtained, and the single-crystal X-ray structure of (2,6-bis{[(pyrid-2-ylmethyl)amino]methyl}pyridine)zinc chloride showed Zn coordination to all five nitrogen atoms. The strong complexation of 2,6-bis{[(pyrid-2-ylmethyl)-amino]methyl}pyridine and (6-{[(pyrid-2-ylmethyl)amino]-methyl}pyrid-2-yl)methanol with Zn II were demonstrated by