The first structural characterization of the proton-ated aza-cyclam ligand in catena-poly[[[(perchlorato)copper(II)]-μ-3-(3-carb-oxy-prop-yl)-1,5,8,12-tetra-aza-3-azonia-cyclo-tetra-deca-ne] bis-(per-chlorate)]

The asymmetric unit of the title com-pound, catena-poly[[[(perchlorato-κO)copper(II)]-μ-3-(3-carb-oxy-prop-yl)-1,5,8,12-tetra-aza-3-azonia-cyclo-tetra-decane-κ4 N 1,N 5,N 8,N 12] bis-(per-chlorate)], {[Cu(C13H30N5O2)(ClO4)](ClO4)2} n , (I), consists of a macrocyclic cation, one coordinated per-chlorate anion and two per-chlorate ions as counter-anions. The metal ion is coordinated in a tetra-gonally distorted octa-hedral geometry by the four secondary N atoms of the macrocyclic ligand, the mutually trans O atoms of the per-chlorate anion and the carbonyl O atom of the protonated carb-oxy-lic acid group of a neighbouring cation. The average equatorial Cu-N bond lengths [2.01 (6) Å] are significantly shorter than the axial Cu-O bond lengths [2.379 (8) Å for carboxyl-ate and average 2.62 (7) Å for disordered per-chlorate]. The coordinated macrocyclic ligand in (I) adopts the most energetically favourable trans-III conformation with an equatorial orientation of the substituent at the protonated distal 3-position N atom in a six-membered chelate ring. The coordination of the carb-oxy-lic acid group of the cation to a neighbouring com-plex unit results in the formation of infinite chains running along the b-axis direction, which are cross-linked by N-H⋯O hydrogen bonds between the secondary amine groups of the macrocycle and O atoms of the per-chlorate counter-anions to form sheets lying parallel to the (001) plane. Additionally, the extended structure of (I) is consolidated by numerous intra- and interchain C-H⋯O contacts.

Crystal structures of trans-di-aqua-(3-R-1,3,5,8,12-penta-aza-cyclo-tetra-deca-ne)copper(II) isophthalate hydrates (R = benzyl or pyridin-3-ylmethyl)

The asymmetric units of the title compounds, trans-di-aqua-(3-benzyl-1,3,5,8,12-penta-aza-cyclo-tetra-decane-κ4 N 1,N 5,N 8,N 12)copper(II) isophthalate monohydrate, [Cu(C16H29N5)(H2O)2](C8H4O4)·H2O, (I), and trans-di-aqua-[3-(pyridin-3-ylmeth-yl)-1,3,5,8,12-penta-aza-cyclo-tetra-decane-κ4 N 1,N 5,N 8,N 12]copper(II) iso-phthalate 0.9-hydrate, [Cu(C15H28N6)(H2O)2](C8H4O4)·0.9H2O, (II) consist of one di-aqua macrocyclic cation, one di-carboxyl-ate anion and uncoordinated water mol-ecule(s). In each compound, the metal ion is coordinated by the four secondary N atoms of the macrocyclic ligand and the mutually trans O atoms of the water mol-ecules in a tetra-gonally distorted octa-hedral geometry. The average equatorial Cu-N bond lengths are significantly shorter than the average axial Cu-O bond lengths [2.020 (9) versus 2.495 (12) Å and 2.015 (4) versus 2.507 (7) Å for (I) and (II), respectively]. The coordinated macrocyclic ligand in the cations of both compounds adopts the most energetically favorable trans-III conformation. In the crystals, the complex cations and counter-anions are connected via hydrogen-bonding inter-actions between the N-H groups of the macrocycles and the O-H groups of coordinated water mol-ecules as the proton donors and the O atoms of the carboxyl-ate as the proton acceptors. Additionally, as a result of O-H⋯O hydrogen bonding with the coordinated and water mol-ecules of crystallization, the isophthalate dianions form layers lying parallel to the (01) and (100) planes in (I) and (II), respectively.

Crystal structure of trans-di-aqua-(3,10-dimethyl-1,3,5,8,10,12-hexa-aza-cyclo-tetra-deca-ne)copper(II) pamoate

The asymmetric unit of the title compound, trans-di-aqua-(3,10-dimethyl-1,3,5,8,10,12-hexa-aza-cyclo-tetra-decane-κ4 N 1,N 5,N 8,N 12)copper(II) 4,4'-methyl-ene-bis(3-hy-droxy-naphthalene-2-carboxyl-ate), [Cu(C10H26N6)(H2O)2](C23H14O6) {[Cu(L)(H2O)2](pam), where L = 3,10-dimethyl-1,3,5,8,10,12-hexa-aza-cyclo-tetra-decane and pam = dianion of pamoic acid} consists of two independent halves of the [Cu(L)(H2O)2]2+ cation and one di-carboxyl-ate anion. The CuII atoms, lying on inversion centres, are coordinated by the four secondary N atoms of the macrocyclic ligands and the mutually trans O atoms of the water mol-ecules in a tetra-gonally elongated octa-hedral geometry. The average equatorial Cu-N bond length is significantly shorter than the average axial Cu-O bond length [2.007 (10) and 2.486 (18) Å, respectively]. The macrocyclic ligand in the complex cations adopts the most energetically stable trans-III conformation. The complex cations and anions are connected via hydrogen-bonding inter-actions between the N-H groups of the macrocycles and the O-H groups of coordinated water mol-ecules as the proton donors and the O atoms of the carboxyl-ate as the proton acceptors into layers lying parallel to the (11) plane.

Recent advances in the intramolecular Mannich reaction in natural products total synthesis

This review focuses on selected applications of the intramolecular Mannich reaction as a key step in the total synthesis of natural products (2000–2017).

Formation and base hydrolysis of oxidimethaneamine bridges in CoIII-amine complexes

cis-[CoL2](3+) (1a(3+)), trans-[CoL2](3+) (2a(3+)), cis-[Co(MeL)2](3+) (1b(3+)), and trans-[Co(MeL)2](3+) (2b(3+)), L = 1,4-diazepan-6-amine (daza) and MeL = 6-methyl-1,4-diazepan-6-amine (Medaza), were allowed to react as templates in acetonitrile with paraformaldehyde and triethylamine. Several Co(III) complexes, where two adjacent amino groups of two ligand moieties are interlinked by an oxidimethaneamine bridge, were obtained. Connection of a primary with a secondary amino group (prim-sec bridging) was found to be predominant. The singly and doubly bridged daza- and Medaza-derivatives 7a(3+), 9a(3+) and 7b(3+), 9b(3+) were characterized by crystal-structure analysis. The bridging process resulted in a slight lengthening of the mean Co-N distance, a red shift of the A1g-T1g transition, and an increase of the Co(III)/Co(II) reduction potential. Several minor components, which could be only partially separated by chromatographic methods, were also formed. The daza-derivatives 6a(3+) (prim-prim bridged) and 10a(3+) (bidentate coordination of one daza frame) formed in small quantities. The Medaza derivatives 3b(3+) and 4b(3+) (trans configuration of the Medaza frames, with additional pending carbinolamino groups), and 8b(3+) (with a methylideneimino group) represent intermediates of the condensation process. Their structure was again corroborated by X-ray diffraction. All bridged species (6a(3+), 7a(3+), 7b(3+), 8b(3+), 9a(3+), 9b(3+), and 10a(3+)) exhibited exclusively a cis orientation of the two diazepane frames, even if the trans configured 2a(3+) or 2b(3+) were used as starting materials. Molecular mechanics calculations indicate that in the bridged species with a trans configuration steric strain is substantially more pronounced. In alkaline aqueous media, 9a(3+) and 9b(3+) revealed a complete degradation of the bridges whereby the original 1a(3+) and 1b(3+) reformed. The pseudo-first-order rate constant k(obs) of the degradation reaction was found to depend linearly on OH(-) concentration. The degradation of the first bridge is about 100 times faster than the degradation of the second. The mechanism of formation and degradation of such oxidimethaneamine bridges is discussed.

Spectroscopic studies, cyclic voltammetry and synthesis of nickel(II) complexes with N(4), N(2)O(2) and N(4)S(2) donor macrocyclic ligands

Nickel(II) complexes of the general composition Ni(L)X(2) (where X=SCN, NO(3) and 1/2SO(4) and ligands=L(1) L(2) and L(3)) have been synthesized and characterized by elemental analyses, magnetic moments, IR, (1)H NMR, (13)C NMR and electronic spectral studies. Nickel(II) ions, such as nitrates, thiocyantes and sulphates were found to act as templates for the cyclic condensations [1+1] and [2+2] of NH(2--)C(6)H(4)--O--CH(2)--CH(2)--O--C(6)H(4)--NH(2), NH(2)--(CH(2))(2)--NH(2) and NH(2)--CH(CH(3))--CH(2)--NH(2) with C(6)H(5)--CO--CO--C(6)H(5), C(6)H(5)--CO--CH(2)--CO--C(6)H(5) and (COOH--CH(2)--CH(2))(2)S. All the complexes show magnetic moments corresponding to two unpaired electrons except [Ni(L(1))](NO(3))(2) and [Ni(L(2))](NO(3))(2) complexes which are diamagnetic. Electronic spectroscopy was used to analyse the differences between the paramagnetic and diamagnetic forms. Electrochemical properties have been studied extensively for Ni(III/II) and Ni(II/I) couples. The equilibrium between the paramagnetic and diamagnetic forms and the nickel(III/II) couple are strongly dependent on the electrolyte. It has been observed that the sulphate group coordinated selectively on the apical position of the nickel(II) centers of the compounds. The structural and electrochemical studies suggest that cooperative effects, involving coordination of sulphate to one nickel center, is responsible for the recognition of this anion. Various ligand field parameters have been calculated and discussed.