Atroposelective Brønsted Acid-Catalyzed Photocyclization to Access Chiral N-Aryl Quinolones with Low Rotational Barriers.

Herein, a novel route to atropisomeric N-aryl quinolones with low rotational barriers is demonstrated, leveraging a dual photochemical/organocatalytic approach to the required ring closure in up to 94% yield and up to >99% ee. The use of a continuous flow system allows for impurity suppression and enables rapid scale-up to a decagram scale.

Synthesis and characterisation of PCsp3P phosphine and phosphinite iridium complexes. Cyclometallation and dehydrogenation of a cyclohexyl ring.

A cyclohexyl based pincer phosphine ligand undergoes cyclometalation with an iridium cyclooctadiene precursor to give a highly thermally stable iridium(III) complex where a C(sp3)-H bond has been oxidatively added. This iridium(III) hydride complex is reduced with potassium to give a terminal iridium(I) dinitrogen complex with no tendency to dimerization. The corresponding cyclohexyl phosphinite ligand undergoes reversible dehydrogenation to give the aromatic cyclometalated iridium(III) hydride complex together with 3 equivalents of dihydrogen.

Trinorsesquiterpenoids from the root extract of Pentalinon andrieuxii.

Two unusual trinorsesquiterpenoids, urechitols A (1) and B (2), were isolated from the root extract of Pentalinon andrieuxii, a plant used commonly in Yucatecan traditional medicine to treat leishmaniasis. The structures of 1 and 2 were identified by interpretation of their spectroscopic data and chemical correlation reactions. The relative stereochemistry of 1 was confirmed through an X-ray crystallographic study.

Synthesis and characterisation of PC(sp3)P phosphine and phosphinite platinum(II) complexes. Cyclometallation and simple coordination.

New and improved preparative routes to the previously known PCP ligands cis-1,3-bis(di-isopropylphosphinito)cyclohexane and cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane are reported. They react with 1 equivalent of dichloro(1,5-cyclooctadiene)platinum(II) [(COD)PtCl2] to give the cis coordinated complex cis-[PtCl2{cis-1,3-bis(di-isopropylphosphinito)}cyclohexane] and the C(sp3)-H activated complex trans-[PtCl{cis-1,3-bis(di-tert-butylphosphino)}cyclohexane]. The new PCP ligand cis-1,3-bis(di-tert-butylphosphinito)cyclohexane was synthesised and reacts with [(COD)PtCl2] giving the di-nuclear trans-[PtCl2{cis-1,3-bis(di-tert-butylphosphinito)cyclohexane}]2, which is highly insoluble. All metal complexes were characterised with X-ray crystallography. DFT calculations indicate that the inability of the phosphinite ligands to cyclometallate is due to a kinetic barrier, possibly involving an axial-equatorial conformational change necessary for the C-H activation process.