Synthesis of fluorinated spiro-1,3-oxazines and thiazines Selectfluor-mediated intramolecular cyclization.

A fluorination-induced intramolecular cyclization for the synthesis of fluoro-substituted spiro-1,3-oxazine and spiro-1,3-thiazine derivatives is described. -(2-(Cyclohex-1-en-1-yl)ethyl)benzamide and benzothioamide are used as the substrates, and the cationic fluorinating agent Selectfluor works as the fluoride source. The reaction yields a single diastereomer.

Magnetically recoverable silica catalysed solvent-free domino Knoevenagel-hetero-Diels-Alder reaction to access divergent chromenones.

A three-component domino Knoevenagel-hetero-Diels-Alder (DKHDA) reaction between 1,3-dicarbonyl, aldehydes/ketones, and alkenes/alkynes leading to the divergent synthesis of chromenones, dihydrochromenones, and spirocyclic chromenones is reported. The reaction was carried out under solvent-free conditions using a magnetically separable silica (Fe3O4@SiO2) catalyst. While two component DKHDA reactions are known, this is the first example of a three component DKHDA reaction involving 1,3-dicarbonyl, ketones, and alkynes producing spirocyclic pyranone derivatives.