... Journal of Sulfur Chemistry. ... A novel series of sulfur-containing dihydrochromeno[8,7-e][1,3]oxazine- 2(8H)-thiones has been synthesized through an eco-friendly Mannich-type condensation cyclization reaction of 7-hydroxy-4-methyl-2-thiocoumarin or 6-chloro-7 ... 2.1. Chemistry. ...