69046-49-7Relevant articles and documents
Calcium-mediated dearomatization, C-H bond activation, and allylation of alkylated and benzannulated pyridine derivatives
Jochmann, Phillip,Leich, Valeri,Spaniol, Thomas P.,Okuda, Jun
, p. 12115 - 12122 (2011)
A facile and general synthetic pathway for the production of dearomatized, allylated, and C-H bond activated pyridine derivatives is presented. Reaction of the corresponding derivative with the previously reported reagent bis(allyl)calcium, [Ca(C3H5)2] (1), cleanly affords the product in high yield. The range of N-heterocyclic compounds studied comprised 2-picoline (2), 4-picoline (3), 2,6-lutidine (4), 4-tert-butylpyridine (5), 2,2′-bipyridine (6), acridine (7), quinoline (8), and isoquinoline (9). Depending on the substitution pattern of the pyridine derivative, either carbometalation or C-H bond activation products are obtained. In the absence of methyl groups ortho or para to the nitrogen atom, carbometalation leads to dearomatized products. C(sp3)-H bond activation occurs at ortho and para situated methyl groups. Steric shielding of the 4-position in pyridine yields the ring-metalated product through C(sp 2)-H bond activation instead. The isolated compounds [Ca(2-CH 2-C5H4N)2(THF)] (2 b·(THF)), [Ca(4-CH2-C5H4N)2(THF)2] (3 b·(THF)2), [Ca(2-CH2-C5H 3N-6-CH3)2(THF)n] (4 b·(THF)n; n=0, 0.75), [Ca{2-C5H3N-4- C(CH3)3}2(THF)2] (5 c·(THF)2), [Ca{4,4′-(C3H5) 2-(C10H8N2)}(THF)] (6 a·(THF)), [Ca(NC13H9-9-C3H 5)2(THF)] (7 a·(THF)), [Ca(4-C3H 5-C9H7N)2(THF)] (8 b·(THF)), and [Ca(1-C3H5-C9H7N) 2(THF)3] (9 a·(THF)3) have been characterized by NMR spectroscopy and metal analysis. 9 a·(THF) 4 and 4 b·(THF)3 were additionally characterized in the solid state by X-ray diffraction experiments. 4 b·(THF)3 shows an aza-allyl coordination mode in the solid state. Based on the results, mechanistic aspects are discussed in the context of previous findings.
