Synthesis of (±)-8-Oxa-3-azabicyclo[3.2.1]octan-2-thione and (±)-2-Oxa-5-azabicyclo[2.2.1]heptan-6-thione: Potential Synthons for the Preparation of Novel Heteroaryl-Annulated Bicyclic Morpholines - Walker, Daniel P.; Wishka, Donn G.; Beagley, Paul; Turner, Gemma; Solesbury, Nicola (Synthesis, 2011)