Synthesis of dipyrrolo[2,3-a:1′,2′,3′-fg]acridin-12(1H)-ones

Acylation reactions of 4,6-dimethoxyindoles with glyoxyloyl chlorides were achieved by the use of graphite powder in 1,2-dichloroethane at reflux. The products were monoketones as a result of decarbonylation, rather than the expected 1,2-diketones. Treatment of these monoketones with base led to their cyclisation and elimination of methanol to afford the novel dipyrrolo[2.3-a:1′,2′,3′-fg]acridin-12(1H)-ones.     

Isolation and characterization of an iodide bridged dimeric palladium complex in carbonylation of methanol

Palladium-catalyzed carbonylation of methanol in presence of iodide promoters was investigated. Iodide bridged palladium dimeric complex, [PPh₃CH₃]₂[Pd₂I₆] was isolated from the carbonylation reaction mixture and characterized using X-ray crystallography. Reaction mechanism was proposed based on IR and UV spectroscopic characterizations of catalytic species involved in the catalytic cycle. The isolated dimeric palladium species, [Pd₂I₆]²⁻ underwent carbonylation to give monomeric species [PdI₃CO]⁻ at atmospheric pressure of carbon monoxide. It was also observed that PPh₃ plays an important role to avoid catalyst deactivation at higher temperatures. Turnover frequency (TOF) of 1052 h⁻¹ was achieved using Pd(OAc)₂-HI-PPh₃ catalyst system at 175 °C.     

Transition Metal Ion-binding Properties of a 14-Membered N2O2S2- Macrobicyclic Ligand

The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N₂O₂S₂-macrobicycle. Metal picrates such as Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺,Cu²⁺ and Cd²⁺ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb²⁺ only among the other metals. The extraction constant (log K _ex) was determined to be 13.8 for Pb²⁺ complex.     

Stereoselective syntheses of unnatural steroidal C(20R) aldehydes by ionic hydrogenation of C-20 tertiary alcohols

Syntheses of three unnatural steroidal C(20R) aldehydes have been realised from 16-dehydropregnenolone acetate. The salient feature of the synthesis is the ionic hydrogenation of C-20 tertiary alcohols leading to the formation of the C(20R) unnatural isomer with complete stereoselectivity. Oxidative hydrolysis of the dithiane moiety furnished the C(20R) aldehydes.     

Dipolar S=O...C=O and C—H...O interactions in the molecular organization of 4,6‐di‐O‐acetyl‐2‐O‐tosyl‐myo‐inositol 1,3,5‐orthoesters

In the absence of conventional hydrogen bonding, the molecules of 4,6‐di‐O‐acetyl‐2‐O‐tosyl‐myo‐inositol 1,3,5‐orthoformate, C₁₈H₂₀O₁₀S, (I), and 4,6‐di‐O‐acetyl‐2‐O‐tosyl‐myo‐inositol 1,3,5‐orthobenzoate, C₂₄H₂₄O₁₀S, (II), are associated via C—H...O interactions. Molecules of (II) are additionally linked via dipolar S=O...C=O contacts. It is interesting to note that the sulfonyl O atom involved in the dipolar S=O...C=O contacts does not take part in any other interaction, indicating the competitive nature of this contact relative to the weak hydrogen‐bonding interactions.     

Concomitant dimorphs of tri-O-[p-halobenzoyl]-myo-inositol 1,3,5-orthoformates with different halogen bonding contacts: first order crystal-to-crystal thermal phase transition of kinetic form to the thermodynamic form

Crystallization of tri-O-[p-halobenzoyl]-myo-inositol 1,3,5-orthoformates from ethyl acetate-petroleum ether solution produced concomitant dimorphs that have different halogen bonding contacts; the kinetic form with C-Br...O-C contacts upon heating to 185 degrees C, converts completely to the thermodynamic form with C-Br...O=C contacts via crystal-to-crystal first order phase transition.     

Nuclear spin-lattice and nuclear spin-spin relaxation time measurements in EuB6 at low temperatures using the spin-echo technique

Experimental results on the nuclear spin-lattice and nuclear spin-spin relaxation times in the ferromagnetic EuB₆ at temperatures below 4·2 K are presented using the external magnetic field,H _ext, in the range of 0 ⩽H _ext ⩽ 10 kG. Nuclear spin-spin relaxation time computed on the basis of the Suhl-Nakamura process turns out to be 3·2μs, which compares well with the experimental value 11·1μs obtained with the 10 kG magnetic field at 1·7 K. It is found that in the ferromagnetic EuB₆,T ₁ is approximately 5 × 10³ times larger thanT ₂ at 1·7 K with the 10 kG magnetic field. Thus the effect ofT ₁ onT ₂ can be neglected. From the experimental value ofT ₂, the value of the homogeneous line broadening is found to be 14 kHz. The corresponding value obtained from the cw method is 175 kHz. This evidently shows the presence of the inhomogeneous line broadening in the cw NMR.