GaCl3- and TiCl4-catalyzed insertion of isocyanides into a C-S bond of dithioacetals

The insertion reaction of isocyanide into a C-S bond of dithioacetals is catalyzed by GaCl3 or TiCl4 to afford thioimidates containing an alpha-alkylthio group. Balanced thiophilicity of these Lewis acids is critical for efficient catalysis.     

Rh(I)-catalyzed reaction of 2-(chloromethyl)phenylboronic acids and alkynes leading to indenes

The reaction of 2-(chloromethyl)phenylboronic acid (1) with alkynes in the presence of a Rh(I) complex gave indene derivatives in high yields. The regioselectivity depends on the steric nature of the substituent on the alkynes. A bulky group favors the alpha-position of indenes.     

Structure of polyethylene sulfide

The structure of the polyether series expressed by the general formula [─(CH₂)_m─O─]_n with m = 1-4, 6, 8-10, and 12 was previously determined [l]. The molecular structure of polyoxymethylene (m = 1) is a sequence of nearly gauche forms (9/5 o r 29/16 helix [a]). On the other hand, the conformation of polythiomethylene, the first member of the polythioether series [─(CH₂)_m ─S─]_n, was found to also be a nearly gauche sequence (l7/9 helix) by Carrazzolo and Valle [3]. Both of these polymers have the highest melting point of each series (polyoxymethylene, 180°C; polythiomethylene, 245°C). Polyethylene oxide (m = 2) is a 7/2 helix consisting of nearly trans, trans, and gauche forms and has rather a low melting point (66°C). Polyethylene sulfide has a very high melting point (210°C) compared with polyethylene oxide. In this respect it is thus of much interest to investigate the structure of polyethylene sulfide. Boileau et al. [4] synthesized high molecular weight polyethylene sulfide and reported its unit-cell dimensions, but they did not determine its structure. In this note, the molecular and crystal structure of polyethylene sulfide is briefly reported.     

Rhodium(I)-catalyzed borylation of nitriles through the cleavage of carbon-cyano bonds

The reaction of aryl cyanides with diboron in the presence of a rhodium/Xantphos catalyst and DABCO affords arylboronic esters via carbon-cyano bond cleavage. This unprecedented mode of reactivity for a borylrhodium species allows the regioselective introduction of a boryl group in a late stage of synthesis.     

Rh(I)-catalyzed silylation of aryl and alkenyl cyanides involving the cleavage of C-C and Si-Si bonds

The Rh(I)-catalyzed silylation of nitriles with disilanes is described. The cleavage of inert carbon-cyano and silicon-silicon bonds occurs in this catalysis.     

Syntheses and magnetic properties of Cu(II)(hfac)2 and Mn(II)(hfac)2 complexes of 4-pyridyl-substituted thioaminyl radicals

Two types of Cu(II)(hfac)2 and Mn(II)(hfac)2 complexes of N-(4-pyridylthio)-4-ethoxycarbonyl-2,6-bis(4-chlorophenyl)phenylaminyl (1) and N-(4-pyridylthio)-2,4,6-tris(4-chlorophenyl)phenylaminyl (2) were prepared and their X-ray crystallographic and magnetic studies were performed. Mixtures of Cu(II)(hfac)2 and 1 and Mn(II)(hfac)2 and 2 in anhydrous heptane-benzene solution gave 1 : 2 complexes of M(II)(hfac)2 (M = Cu, Mn) and 1 or 2 in 73-75% yields. For Cu(II)(hfac)2(1)2 and Mn(II)(hfac)2(2)2 X-ray crystallographic analyses were successfully performed. The magnetic behaviors for the two metal complexes were investigated with a SQUID magnetometer. The analyses for the chimolTvs. T plots of Cu(II)(hfac)2(1)2 were carried out by the numerical diagonalization of the Heisenberg Hamiltonian matrix (4096 x 4096 matrix) for the four repeating units of the complex (12-spin system). The exchange interaction between the copper(II) ion and the thioaminyl radicals is ferromagnetic (J1/kB = +28 K) and the interactions between the complexes is antiferromagnetic (J2/kB = -13 K). The magnetic behavior of Mn(II)(hfac)2(2)2 complexes is well analyzed with the theoretical equation of a 1/2-5/2-1/2 three-spin system taking the intermolecular interaction (theta) into account. The exchange interaction between the Mn(II) ion and the thioaminyl radicals is antiferromagnetic (J/kB = -4.2 K) and theta = -1.0 K. These magnetic behaviors could be well explained in terms of their crystal structures.     

Rhodium-catalyzed reaction of terminal alkynes with allylamine leading to (E)-3-alkylidene N-heterocycles

Terminal alkynes react with allylamine in the presence of a RhCl(PPh3)3 catalyst to give (E)-3-alkylidene-3,4-dihydro-2H-pyrroles. The products consist of two molecules of alkyne and one molecule of allylamine. Although dimers, trimers, and oligomers of alkynes are also obtained as byproducts, the addition of various ammonium salts to the reaction suppresses such oligomerization, resulting in an increase in product.     

Rhodium-catalyzed synthesis of germoles via the activation of carbon-germanium bonds

The rhodium-catalyzed reaction of 2-germylphenylboronic esters with alkynes in the presence of a rhodium(I) catalyst is established as a modular method for the synthesis of an array of benzogermole derivatives. The reaction proceeds through the activation of C(sp(3))-Ge bonds. The mechanism of this new bond activation process is discussed based on the activation aptitude of alkyl and aryl substituents on germanium.