MECHANISM OF BIOMIMETIC OXIDATION OF CYCLOHEXANE TO CYCLOHEXANONE BY HYDROGEN PEROXIDE

The process of gas-phase oxidation of cyclohexane was studied in the presence of a heterogeneous biomimetic catalyst (per-FTPhPFe(III)OH/Al2O3), at 130–2500C, in which high yields of cyclohexanone and cyclohexanol were obtained up to 25.2% with a selectivity of ~80% at a cyclohexane conversion of 34%. The mechanism of the conversion of cyclohexane to cyclohexanone has been studied in detail, and the coherently synchronized character of the reaction proceeding is shown

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

New chiral regioisomeric γ-hydroxyphosphine ligands were synthesized from α-pinene. The key transformation was the thermal [2,3]-sigmatropic rearrangement of allyldiphenylphosphinites, obtained from (1R,2R,4S,5R)-3-methyleneneoisoverbanol and (1R,2R,3R,5R)-4-methyleneneoisopinocampheol, to allylphosphine oxides. Hydroxy groups were introduced stereoselectively through a hydroboration–oxidation reaction proceeding from the less hindered site providing a trans relationship between the hydroxy and the phosphine substituents.

Why are reactions of 2- and 8-thioquinoline derivatives with iodine different?

The crystal structures of 1,2-dihydro-1,1′-bi[thiazolo[3,2-a]quinoline]-10a,10a′-diium diiodide hemihydrate, C22H16N2S2 2+·2I−·0.5H2O, and 1,2-dihydro-1,1′-bi[thiazolo[3,2-a]quinoline]-10a,10a′-diium iodide triiodide, C22H16N2S2 2+·I−·I3 −, obtained during the reaction of 1,4-bis(quinolin-2-ylsulfanyl)but-2-yne (2TQB) with iodine, have been determined at 120 K. The crystalline products contain the dication as a result of the reaction proceeding along the iodocyclization pathway. This is fundamentally different from the previously observed reaction of 1,4-bis(quinolin-8-ylsulfanyl)but-2-yne (8TQB) with iodine under similar conditions. A comparative analysis of the possible conformational states indicates differences in the relative stabilities and free rotation for the 2- and 8-thioquinoline derivatives which lead to a disparity in the convergence of the potential reaction centres for 2TQB and 8TQB.

Epoxides as Precursors to 1-Hydroxymethyl Indolizidine and Pyrrolizidine

Herein we describe the synthesis of 1-hydroxymethyl pyrrolizidine and indolizidine alkaloids from epoxy-tethered pyrrole precursors. Two titanium-based methods are evaluated for the construction of the bicyclic scaffold: the Lewis acid mediated cyclization developed by Tanis and Raggon and the titanocene(III)-catalyzed reaction proceeding via radical intermediates. The former method, after hydrogenation of the pyrrole moiety, ultimately gives rise to enantiopure (–)-tashiromine, being the most concise and atom-economic procedure reported to date.

A convenient protection for 4-oxopyrimidine moieties in nucleosides by the pivaloyl group

Application of the pivaloyl group as a protection for the N3 position of thymidine and uridine was investigated. Pivaloylation of thymidine is a very rapid reaction proceeding under mild conditions with excellent regioselectivity for sugar or thymine moiety, depending on the amines used. Several pivaloylated thymidine derivatives were obtained by treatment of unprotected thymidine with pivaloyl chloride under various experimental conditions. Stability of the N3-pivaloyl protecting group under basic and acidic conditions was evaluated and the conditions for its selective removal were found.