Studies of dithiiranes and thiosulfines as reactive intermediates

Indirect, but compelling evidence for the intermediacy of dithiiranes 1 and thiosulfines 2 has been found by us and is also provided by literature data. The intriguing dithiirane → dithioester rearrangement as well as most of the interrelations and conversions postulated in Scheme 1 have been demonstrated experimentally. In a number of cases acetyl α-chloroalkyl disulfides 16 (X = Cl, Y = COCH₃) are useful starting materials for the synthesis of thioamides such as 40.     

Synthese d'aminophosphinephosphinites chiraux. Utilisation en reduction asymetrique catalytique

The chiral aminophosphinephosphinites ligands (AMPP) are directly synthesized from natural amino alcohols or by reduction of formyl esters of α-amino acids and PPh₂Cl. Their cationic rhodium complexes have been found to be excellent catalysts for enantioselective hydrogenation of dehydroamino acids (ee ∼ 86%, yield ∼ 100%) for example. Asymmetric reduction of ketones can also be performed with the new alkyl AMPP* modified rhodium catalyst (ee 50%).     

Crystal and molecular structure of {3-[t-butyl(phenyl)phosphino]propyl}dimethyltin chloride

{3-[t-Butyl(phenyl)phosphino]propyl}dimethyltin chloride crystallizes in the space group P2₁/a. The unit cell, with a 22.798(9), b 9.578(4), c 8.385(7) Å, β 102.16(3)°, V 1789.9(26) ų, contains 4 discrete molecules. The structure was refined to a final R value of 0.040. The tin atom has a distored trigonal bipyramidal environment with the phosphorus and chlorine atom in axial positions. The tin-phosphorus intramolecular interaction distance is 3.078(2) Å.     

Tailoring Pore Structure and Morphologies in Covalent Organic Frameworks for Xe/Kr Capture and Separation

As a rising star among porous solid materials, covalent organic frameworks(COFs) with excellent properties including but not limit to facilely controllable structure, high porosity, and multi-chemical functionality represent significant potential for efficient ¹²⁷Xe/⁸⁵Kr capture and separation. In this study, through tuning the length of the organic ligands, two-dimensional(2D) COF mate-rials with identical connection group but different pore properties, denoted as ATFG-COF and TpPa-COF with AA-stacking model and TpBD-COF with AB-stacking model were synthesized and tested for Kr and Xe adsorption for the first time. Adsorption measurements indicate that the narrower pore apertures and higher porosity are conducive for COF materials to capture Xe and Kr. Furthermore, the Henry's constant, isosteric heat of adsorption(Q_st), and ideal adsorbed solution theory(IAST) selectivity of ATFG-COF, the pore size of which is closest to the kinetic diameter of the Xe atom(0.41 nm) among 2D COF materials, were carried out based on the single component sorption isotherms. The results illustrate that the high isosteric heat values of Xe/Kr adsorption on ATFG-COF are 25 and 16 kJ/mol at room temperature, respectively. Henry's law predicts that the selectivity factor of Xe to Kr is 6.07, consistent with the adsorption selectivity(ca. 6) calculated based on the IAST.     

Laser induced synthesis: Condensation of acrylonitrile on mesityl oxide

The photoaddition of acrylonitrile to mesityl oxide was accomplished at 355 nm with high quantum yield (15%) using a pulsed laser (intensity= 9 MW/cm², pulse duration 13 ns, repetition rate= 10Hz) and selectively led to three products in contrast to irradiation with a mercury lamp which principally gave an acrylonitrile polymer and with continuous wave laser (intensity= 5.7 W/cm²) which gave a much lower quantum yield (0.4%).     

D3-trishomocubanetrione synthesis and optical resolution

A large-scale synthesis for the title compound rac-1 based on 11-oxahexacyclo-[5.4.1.0^2,6.0^3,10.0^4,8.0^9,12] dodecan-5-one (12) as the key intermediate and an efficient procedure for the optical resolution of rac-1 via the diastereomeric ketals with (R,R)-2,3-butandiol are reported. The absolute configuration is established by correlating the optically pure (+)-trione ([α]_D +949°) with (-)-trishomocubane.     

An approach to eriolanin. Synthesis of α-methylene lactones of trans-1,3-dihydroxycyclohexanes

A new synthesis of α-methylene lactones is discussed which incorporates an intramolecular epoxide opening with a vinyl anion.     

Synthesis of an azulene lactone by an intramolecular [6+4] cycloaddition

Intramolecular cycloadditions of 6-fulvenyl 2.2-dimethyl-3,5-hexadienoate produce both [6+4] and [4+2] adducts. The [6+4] adduct can be converted into an azulene lactone. Less highly substituted fulvenyl diene esters give analogous products in modest yields.