1 -Methyl-1,4-dihydropyridine, calculated

Recently reported has been a comprehensive experimental and theoretical study of the Diels-Alder reaction of 1,2-dihydropyridines such as 56, 94 and 112 with numerous dienophiles to form 2-azabicyclo[222]octenes <2007JOC3458>. It was discovered that in all cases the kinetic preference was for the endo-aAAuct. Theoretical calculations showed that for the dienophile methyl vinyl ketone the total transition state energy favored the... 

Calculations on the dihydro forms corresponding to 2-PAM indicate that the structural assignment (3) is supported by the calculations according to which the 1,6-dSiydro form is the base form of the 1-methyl-l, 6-dihydropyridine-2-carbaldoxime (Pro-2-PAM) which corresponds to the protonated 3,6-dihydro structure XVIII. It was also found that the initial syn-anti energy difference in the case of 2-PAM disappeared when the corresponding dihydro derivatives are formed. 

Figure 8. Calculated geometry of the most stable form of axiti-l-methyl-1,6-dihydropyridine-2-carbaldoxime (XVI). The oxime group is rotated 86° from the plane of the ring and the oxime hydrogen is trans and planar with the oxime function. The methyl hydrogens are rotated 25,145, and 265° with respect to the ring. The ring is essentially planar.

Theoretically calculated IR spectra of the l-methyl-4-[2-(4-hydroxyphenyl)ethe-nyl)]pyridinium] cation and l-methyl-4-[2-(4-oxocyclohexadienyliden)ethyliden]-l,4-dihydropyridine support the elucidation of the experimental IR bands. The highest frequency band in the IR spectrum of the cation at 3490 cm" corresponds to the Vqh mode (Figure 6.13). The low-intensive bands within the 3055 to 3000 cm" range are... 

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