Synthesis of Sulfur-Substituted Quinolizidines and Pyrido[1,2-a]azepines byRing-Closing Metathesis. -The heterocyclic frameworks are prepared using the first generation Grubbs catalyst at room temperature. Only product (IIc) requires refluxing toluene conditions and is obtained in low yield.
We have developed a solvent‐free phase‐transfer catalysis (PTC) method for the N‐alkylation of sulfur‐substituted dihydropyridone 4a to give products 5 with varying side‐chains and functional groups. Treatment of the chlorides 5a and 5c with NaI in acetone at reflux gave high yields of the iodides 6a and 6b. The reaction of iodides 7a and 7b with t‐BuLi at low temperature, followed by sequential treatment with HOAc and NaBH4, resulted in the formation of quinolizidine 8a and pyridoazepine 8b, respectively. Similar reaction of bromide 5j with t‐BuLi gave indolizidine 11.
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