N-Prop-2-ynylmaleimide. Application to Sequential One-pot Rh(I) Catalysed [2+2+2]-Alkyne Cyclotrimerisation–Imine Cycloaddition

The Asymmetric Transfer Hydrogenation of Benzoylpyridine: Preparation and Crystal Structure of Chiral Heterocyclic Schiff Base Ligands

Two optically active heterocyclic imine ligands 3 (3a and 3b) have been synthesised for the iridium catalysed asymmetric transfer hydrogenation of 4-benzoylpyridine. 3b was characterised by single crystal X-ray diffraction analysis. The two ligands (3a and 3b) were applied to Ir-catalysed asymmetric transfer hydrogenation of 4-benzoylpyridine using 2-propanol as a source of hydrogen. The results showed that the corresponding chiral alcohol could be obtained with moderate yield and enantioselectivity at an optimum temperature.

Chemo- and Regioselective Intermolecular Cyclotrimerization of Terminal Alkynes Catalyzed by Cationic Rhodium(I)/Modified BINAP Complexes: Application to One-Step Synthesis of Paracyclophanes

A highly regioselective intermolecular cyclotrimerization of terminal alkynes has been developed based on the use of the cationic rhodium(I)/DTBM-Segphos complex. This method can be applied to a variety of terminal alkynes to provide 1,2,4-trisubstituted benzenes in high yield and with high regioselectivity. A chemo- and regioselective intermolecular crossed-cyclotrimerization of dialkyl acetylenedicarboxylates with a variety of terminal alkynes has also been developed based on the use of the cationic rhodium(I)/H8-BINAP complex, furnishing 3,6-disubstituted phthalates in high yields. It constitutes a highly efficient new method for intermolecular crossed-cyclotrimerization of two different monoynes in terms of catalytic activity, chemo- and regioselectivity, scope of substrates, and ease of operation. The versatility of this new crossed-alkyne cyclotrimerization procedure is demonstrated through its application to one-step synthesis of a [6]metacyclophane and [7]-[12]paracyclophanes from the corresponding terminal alpha,omega-diynes. Mechanistic studies have revealed that the chemo- and regioselectivity of this crossed-alkyne cyclotrimerization are determined by the preferential formation of a specific rhodium metallacycle derived from a terminal alkyne and a dialkyl acetylenedicarboxylate.

Synthesis of monodisperse oligo-p-phenylenes via rhodium-catalyzed alkyne cyclotrimerization

[structure: see text] A novel synthesis of monodisperse oligo-p-phenylenes is described that features alkyne cyclotrimerization of ether-linked p-dialkynylarenes. This route introduces solubilizing dihydrofuran and alcohol functional groups that may improve processing of the corresponding polymeric p-phenylene materials.