GHOSH, M. K.; ROUT, N.; GIRI, S.; RSC Adv. 6 (2016) 32, 26886-26894, http://dx.doi.org/10.1039/C6RA00036C ; Dep. Chem., Natl. Inst. Technol., Rourkela 769 008, Odisha, India; Eng.) -M. Tismer 30-043

Facile generation of quaternary carbon centres has been realised in the presence of phenyl trimethyl ammonium tribromide (PTAB) mediated oxidative dearomatisation.

An open air ruthenium­(VIII)-catalyzed oxidative spiro-etherification as well as spiro-amidation of phenols has been performed. The transformation works satisfactorily with both phenols and naphthols and thus exhibits a wide range of flexibility. The catalysis is performed in open air at room temperature with a yield of ≤95%.

This paper entails the first recognition of Phenyl Trimethyl Ammonium Tribromide (PTAB) as an effective reagent for spiro-cyclizations proceeding via oxidative dearomatization. The experiment exhibits economical, metal and ligand free one-pot accomplishment of these significant transformations. The described protocol presents the first generalised methodology of spiro-oxacycle synthesis which can be applied towards various directions. A stereoselective synthesis of oxa-spirocyclooxadieneones has been accomplished.

Xyloketals, unique bioactive compounds, isolated from mangrove fungus Xylaria sp. (no. 2508), having multiple pharmacological, therapeutic properties, have prompted enormous research on their stereochemistry, bioactivity and synthetic attempts made toward this novel family. This review brings forward a systematic and comprehensive survey of the method of both racemic and enantioselective synthesis, reactivity, and biological properties associated with the xyloketal derivatives and their analogues.