We report the synthesis of both macrocyclic and linear derivatives of pyrrole-2,5-diacetic bisamides, and the studies of their anion binding properties, which are further compared with the properties of similar derivatives bearing dipicolinic or isophthalic moieties. The new macrocyclic compound built on pyrrole-2,5-diacetic bisamide was found to be an efficient receptor for H2PO4 and PhCOO , e...

An electron-withdrawing group was introduced to the α-position of chalcones, and the resulting alkylidene diketones showed new reactivities with enals under the catalysis of N-heterocyclic carbenes (NHCs). Selective activation of enals affords enolate equivalents that undergo highly enantioselective intermolecular Diels-Alder reactions with the alkylidene diketones. No products that might have ...

Density functional theory calculations were used to predict the behaviour of a potential novel architecture of olefin metathesis catalysts, in which one of the neutral ligands of classical Ru-based catalysts, e.g. a phosphine or an N-heterocyclic carbene, is replaced by an alkylidene group. Introduction of a second alkylidene ligand favors dissociation of the remaining phosphine and the overall...

This short review article covers some useful applications of alkynyltungsten compounds to the syntheses of complex lactones. Two types of cyclizations will be emphasized: (1) cycloalkenylation of tungsten-alkynol compounds with aldehydes to give α-alkylidene oxacarbeniums, further leading to α-alkylidene lactones and (2) intramolecular [3+2]-cycloaddition of epoxides to give bicyclic lactones. ...

The first structurally authenticated yttrium-alkyl-alkylidene is reported; structural, spectroscopic, and theoretical analyses show that whilst the yttrium-alkylidene bond is short, it possesses a bond order less than one and is comparable to the Y-C(alkyl) single bond within the same molecule.

Alkylidene carbenes undergo rapid inter- and intramolecular reactions rearrangements, including 1,2-migrations of β-substituents to generate alkynes. Their propensity for substituent migration exerts profound influence over the broader utility alkylidene carbene intermediates, yet prior efforts categorize 1,2-migratory aptitude in these elusive species have been hampered by disparate modes gene...

A stereoselective cyclization between alkylidene oxindoles and 5-methoxyoxazoles has been developed using catalytic titanium(IV) chloride (as low as 5 mol %) to afford spiro[3,3'-oxindole-1-pyrrolines] in excellent yield (up to 99%) and diastereoselectivity (up to 99:1). Using a chiral scandium(III)-indapybox/BArF complex affords enantioenriched spirooxindole-1-pyrrolines where a ligand-induced...

The redox potentials of 4,4’-dimethyl-N’N’-alkylidene bridged 2,2’-bipyridinium salts derivatives (DBPAs) can be controlled by changing the N, N’-alkylidene bridge length which changes the conformation of the DBPAs.. In this paper, the torsional angles between the two pyridine rings and the molecular energy of DBPAs are calculated using a PC based software package (AccuModel 1.2). The relations...