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)]
CAN 91:56710 27-1 Heterocyclic Compounds (One Hetero Atom) Inst. Chim. Org.,Univ. Lausanne,Lausanne,Switz. Journal 0044-8249 written in German. 289-65-6; 16855-95-1; 30958-75-9; 33666-44-3; 51483-74-0; 57147-16-7; 70287-81-9; 70287-82-0 Role: RCT (Reactant), RACT (Reactant or reagent) (metalation of); 19150-07-3P; 70287-77-3P; 70287-78-4P; 70287-79-5P; 70287-80-8P; 70287-83-1P; 70287-84-2P; 70287-85-3P; 70287-86-4P; 70287-87-5P; 70287-88-6P; 70287-89-7P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. of)
Record created on 2006-03-03, modified on 2016-08-08