Tetrahydropyridinium salts

Depending upon the structure of the substrates 49, 52, and 56 hexahydropyrido[l,2-n]-[3,l]benzoxazines 50, 54, 2-aminobenzaldehyde 53, 1-substituted piperidones 51, 55, 57, 3,4,5,6-tetrahydropyridinium salt 58, or their mixture was obtained during the oxidation of 1-(2-hydroxymethyl-, 2-formyl- and 2-acetylphenyl)piperazines (49, 52, 56) with Hg(II)-EDTA complex (Schemes 6-8) (79AP219, 98ZN(B)37, 98ZN(B)1369). 

Silicon-induced fragmentations.2 Treatment of the tetrahydropyridinium salt 1 with CsF in CH3CN results in a stereoselective fragmentation to the (2Z,5E)-heptadiene 2. In contrast, the N-oxide 3 fragments spontaneously to the (Z,Z)-heptadiene 4. This fragmentation has been used to obtain (E,E)- and (E.Z)-dienes.3... 

Review "Nucleophilic Additions to Tetrahydropyridinium Salts Applications to Alkaloid Syntheses"... 

Tetrahydropyridinium salts, stereochemistry of nucleophilic addition to 84MI28. 

Synthetic aspects of alkaloid photochemistry 80CRV269. Tetrahydropyridinium salts in alkaloid synthesis 84ACR289. 

Alkaloids, synthesis from tetrahydropyridinium salts 84ACR289. 

An ion pair mechanism has also been invoked to account for the 1,2 and 1,4 rearrangements which are observed when tetrahydropyridinium salts are heated with phenyllithium in ether 76>. 

The key intermediates, A -(arylsulfonyl)tetrahydropyridinium salts (259), were regiospecifically obtained by triflate-assisted decarbonylation reaction from (258). The final step to (260) is a nucleophilic-electrophilic exo-tet type cyclocondensation process (Scheme 26) <90JCS(Pt)l835>. 

Stevens RV (1984) Nucleophilic additions to tetrahydropyridinium salts. Applications to alkaloid syntheses. Acc Chem Res 17 289-296... 

Unsaturated tertiary amines are the products of the Hofmann degradation of l,2-dialkyl-l,2,3,6-tetrahydropyridinium salts and of the reduction of tertiary propargylamines with DIBAL. ... 

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