Tetrahydropyridines, synthesis

The proton NHR spectrum of the crude buten-l-ol was essentially identical to that of the distilled product, except for traces of solvent. This crude silylbuten-l-ol was of sufficient purity for the tetrahydropyridine synthesis described in the next procedure. 

Regioselective Synthesis of Tetrahydropyridines. Synthesis of l-(4-Methoxyphenyl )-l, 2, 5,6-tetrahydropyridine... 

The submitters report that Z-4-(trimethylsilyl)-3-buten-l-ol of >98% isomeric purity can be obtained in ca. 60% overall yield by a more lengthy sequence involving hydroalumination-protonolysis of the tetrahydropyranyl (THP) ether of 4-(trimethylsilyl)-3-butyn-l-ol followed by cleavage5 of the THP ether with pyrldinium p-toluenesulfonate in methanol. This sequence is less convenient for the tetrahydropyridine synthesis described In the next procedure, since the Isomeric purity of the vlnylsilane is not Important for the cycllzatlon reaction.6... 

A particularly useful general method for the synthesis of 5- to 7-membered partially unsaturated heterocycles is the Grubbs olefin metathesis applied to acyclic dialkenyl amines, as illustrated by the tetrahydropyridine synthesis shown below7 ... 

Synthesis of Pyridine Derivatives. Tetrahydropyridine derivatives are readily formed by Diels-Alder cycloadditions of a 1-azadiene with activated alkenes. A review makes clear the many uses of this type of heterodiene in Diels-Alder and other heterocycle-forming processes. An example of tetrahydropyridine synthesis is shown in Scheme 5.4. 

Scheme 14.20 One-pot tetrahydropyridine synthesis by tandem Stille coupling/ aza-electrocyclization process.

Koldobskii, A.B., Solodova, E.V. and Kalinin, V.N. (2011) Addition reactions of 1,1, l-trifluoro-4-trimethylstannylbut-3-yn-2-one and 1,1, l-trifluorobut-3-yn-2-one to some tetrahydropyridines. Synthesis of trifluoroacylated polysubstituted tetrahy-droazocines. Russian Chemical. Bulletin, 60(5), 1010-1013 Izvestiya Akademii Nauk. Seriya Khimicheskaya, 60(5), 988-991 Cheminform, 2011, 42(17), doi 10.1002/chin.201117177... 

---