Metalation of Pyrans and Dihydropyridines : When is an 8pi-System Cost Effective ?

The pyrans I (R = Me, H; R1 = H) with BuLi/KOCMe3 or KSiMe3 gave the 2-metalated derivs. I (R1 = K), which reacted with alkyl halides to give I (R = H, Me; R1 = Me, Et, SiMe3, CH2SiMe3); thus the behavior the 4H-pyrans toward organometallic reagents is similar to that of 3,4-dihydro-2H-pyrans. The pyridine II (R2 = Me, R3 = H) was metalated with BuLi/KOCMe3 only in the 2-position to give II (R3 = H), whereas the metalation position of II (R2 = R3 = H) depends on the reagent; thus, II (R2 = R3 = H) reacted with BuLi/KOCMe3 and MeI to give II (R2 = H, R3 = Me), whereas with KSiMe3 in THF and MeO gave a 1:1 mixt. of II (R2 = H, R3 = Me) and II (R2 = Me, R3 = H). This is the first example of proton removal from the allylic position of a dihydropyridine to form an organometallic 8p system. [on SciFinder (R)]