Pyrolysis—gas chromatographic determination of run numbers in methyl methacrylate--styrene copolymers using the boundary effect

By considering the effect of neighbouring monomer units in depropagating polymer chain radicals on the formation of degradation products, a new boundary effect theory was developed in order to elucidate the sequence distributions in vinyl-type copolymers using the corresponding monomer yields. This theory was applied succesfully to the calculation of the sequence distributions in methyl methacrylate—styrene copolymers in terms of the run numbers. The significance of newly introduced parameters (monomer formation probability constants) is also discussed.     

Photocatalytic hydroxylation of aromatic ring by using water as an oxidant

Electrophilic oxygen species photocatalytically derived from water molecules can selectively react with the aromatic ring of both benzene and its derivatives to produce the corresponding phenols and hydrogen over platinum-loaded titanium oxide when illuminated with light of appropriate wavelength in the absence of oxygen.     

Rhodium/chiral diene-catalyzed asymmetric 1,4-addition of arylboronic acids to arylmethylene cyanoacetates

Asymmetric 1,4-addition of arylboronic acids to (E)-methyl 2-cyano-3-arylpropenoates proceeded in the presence of a rhodium catalyst (3 mol %) coordinated with a chiral diene ligand, (R,R)-Ph-bod*, to give high yields of the corresponding methyl 3,3-diaryl-2-cyanopropanoates with high enantioselectivity (up to 99% ee). This catalytic asymmetric transformation was applied to the asymmetric synthesis of (R)-tolterodine.     

Base‐Free Conditions for Rhodium‐Catalyzed Asymmetric Arylation To Produce Stereochemically Labile α‐Aryl Ketones

The asymmetric arylation of 2,2‐dialkyl cyclopent‐4‐ene‐1,3‐diones with aryl boronic acids was found to be efficiently catalyzed by a chiral diene–rhodium μ‐chloro dimer, [{RhCl((R)‐diene*)}₂], in the absence of bases in toluene/H₂O to give 2,2‐dialkyl 4‐aryl cyclopentane‐1,3‐diones in high yields with high enantioselectivity. Such compounds can not be obtained with high enantiomeric purity under the standard basic conditions used for rhodium‐catalyzed asymmetric arylation because the α‐aryl ketone products undergo racemization under the basic conditions.     

Palladium-catalyzed synthesis of spiro[2.4]heptanes: ligand-dependent position control in the nucleophilic attack to a pi-allylpalladium intermediate

A palladium-catalyzed intermolecular cycloaddition of gamma-methylidene-delta-valerolactones with electron-deficient olefins has been developed for the synthesis of spiro[2.4]heptanes with high selectivity through a nucleophilic ring closure to the central carbon of a pi-allylpalladium intermediate. It was found that the course of the reaction is dependent on the ligand employed, and selective [4 + 2] cycloadditions can also be achieved by the use of a bulky monophosphine ligand.     

Iron-catalyzed arylmagnesiation of aryl(alkyl)acetylenes in the presence of an N-heterocyclic carbene ligand

Addition of arylmagnesium bromides to aryl(alkyl)acetylenes proceeded in the presence of an iron catalyst and a N-heterocyclic carbene ligand to give high yields of the corresponding alkenylmagnesium reagents, which were transformed into tetrasubstituted alkenes by subsequent treatment with electrophiles. [reaction: see text]