Abstract
Isothiourea‐Mediated One‐Pot Synthesis of Functionalized Pyridines
Highlights
Pyridines are an extremely privileged heterocyclic class commonly found in natural products and functional materials
The increased temperatures are necessary to promote effective N- to O-sulfonyl migration in this process, with lower temperatures leading to mixtures of the intermediate pyridone and desired pyridine
Trifluoromethyl-containing a,b-unsaturated ketimines were readily prepared from the corresponding enones and used in this protocol, giving pyridines in acceptable yields (40–66 %; Table 3)
Summary
Pyridines are an extremely privileged heterocyclic class commonly found in natural products and functional materials. Subsequent addition of the a,b-unsaturated ketimine 5[13] in the presence of the isothiourea DHPB (6; 20 mol %) in CH2Cl2 at 0 8C for 4 hours afforded the pyridine 7 in only 7 % yield after chromatographic purification,[14] despite complete consumption of 5 (Table 1, entry 1). Optimization of this process showed that a combination of increased temperature and changing the solvent gave a higher yield of the isolated pyridine (entries 2–4).
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