Unusual In2N4 cores in complexes containing triazole-based chalcogen-phosphoranyl ligands

The 4,5-bis(diphenylphosphoranyl)-1,2,3-triazole [4,5-(P(E)Ph2)2tz] derivatives of indium {kappa3-N,N',E-[4,5-(P(E)Ph2)2(mu-tz)]InMe2}2 (E = O2, S3, Se4) were prepared in good yield. In addition, compound 5 (E = O, E' = Se) was obtained from 4 through the replacement of a selenium atom in the P-Se(In) moiety by an oxygen atom, giving the mixed-chalcogen complex. The crystal structures of 2 and 5 exhibit a central C4In2N6O2P4core with an almost planar arrangement (mean deviation = 0.019 and 0.042 A for 2 and 0.100 A for 5), while the C4In2N6S2P4 core in 3 is nonplanar (mean deviation = 0.223 A).     

C-H Bond Functionalization via Hydride Transfer: Formation of α-Arylated Piperidines and 1,2,3,4-Tetrahydroisoquinolines via Stereoselective Intramolecular Amination of Benzylic C-H Bonds

We here report a study of the intramolecular amination of sp(3) C-H bonds via the hydride transfer cyclization of N-tosylimines (HT-amination). In this transformation, 5-aryl aldehydes are subjected to N-toluenesulfonamide in the presence of BF(3)·OEt(2) to effect imine formation and HT-cyclization, leading to 2-arylpiperidines and 3-aryl-1,2,3,4-tetrahydroisoquinolines in a one-pot procedure. We examined the reactivity of a range of aldehyde substrates as a function of their conformational flexibility. Substrates of higher conformational rigidity were more reactive, giving higher yields of the desired products. However, a single substituent on the alkyl chain linking the N-tosylimine and the benzylic sp(3) C-H bonds was sufficient for HT-cyclization to occur. In addition, an examination of various arenes revealed that the electronic character of the hydridic C-H bonds dramatically affects the efficiency of the reaction. We also found that this transformation is highly stereoselective; 2-substituted aldehydes yield cis-2,5-disubstituted piperidines, while 3-substituted aldehydes afford trans-2,4-disubstituted piperidines. The stereoselectivity is a consequence of thermodynamic control. The pseudoallylic strain between the arene and tosyl group on the piperidine ring is proposed to rationalize the greater stability of the isomer with the aryl ring in the axial position. This preferential placement of the arene is proposed to affect the observed stereoselectivity.     

Catalytic coupling of arene C-h bonds and alkynes for the synthesis of coumarins: substrate scope and application to the development of neuroimaging agents

C-H bond functionalization offers strategically novel approaches to complex organic compounds. However, many C-H functionalization reactions suffer from poor compatibility with Lewis basic functional groups, especially amines, which are often essential for biological activity. This study describes a systematic examination of the substrate scope of catalytic hydroarylation in the context of complex amino coumarin synthesis. The choice of substrates was guided by the design and development of the next generation of fluorescent false neurotransmitters (FFNs), neuroimaging probes we recently introduced for optical imaging of neurotransmission in the brain. Comparison of two mild protocols using catalytic PtCl(4) or Au(PPh(3))Cl/AgSbF(6)revealed that each method has a broad and mutually complementary substrate scope. The relatively less active platinum system out-performed the gold catalyst with indole substrates lacking substitution at the C-3 position and provided higher regioselectivity in the case of carbazole-based substrates. On the other hand, the more active gold catalyst demonstrated excellent functional group tolerance, and the ability to catalyze the formation of strained, helical products. The development of these two protocols offers enhanced substrate scope and provides versatile synthetic tools required for the structure-activity examination of FFN neuroimaging probes as well as for the synthesis of complex coumarins in general.     

Taxicab geometry in table of higher-order elements

Nonlinear Dynamics - The paper deals with the analysis of the order of the differential equation of motion describing the dynamics of a one-port network compounded of series or parallel connections...     

1.2 Anorganische Analyse

Ohne Zusammenfassung     

1.2 Anorganische Analyse

Ohne Zusammenfassung     

Sums of continuous and differentiable functions in dynamical systems

We investigate stability of Martin boundaries for positive solutions of elliptic partial differential equations. We define a perturbation which isG _L ^D -semismall at infinity, show that Martin boundaries are stable under this perturbation, and give sufficient conditions for it. This work was carried out partially while the author was visiting the Department of Mathematics, Technion — Israel Institute of Technology. He wishes to thank the Israel Association for the Promotion of International Scientific Relations, the Japan Society of Promotion of Science, and the Technion.