Asymmetric Synthesis of 2-Alkyl(Aryl)-2,3-dihydro-4-pyridones by Addition of Grignard Reagents to Chiral 1-Acyl-4-methoxypyridinium Salts

Regioselective addition reactions at C-2 of 3,4-dihydropyrimidinones. Synthesis and evaluation of multifunctionalized tetrahydropyrimidines

“…The reaction of phenylmagnesium bromide with 10 was also very facile and furnished the pyrimidine derivative 12j in 68% yield. While the deprotection of carbamate from N-3 positions of products 12aej using LiAlH 4 in methanol 17 (stirring at 0 C to room temperature and then reflux), NaOMe in refluxing methanol 33 or tetrabutyl ammonium fluoride (TBAF) in THF 34 could not be achieved, the current methodology served the purpose of appending a variety of substituents at the C-2 position, regioselectively and in a synthetically useful manner. The formation of the products 12 and 15 can be visualized to be proceeding through the mechanism shown in Scheme 2.…”

Diastereoselective radical cyclization reactions: the synthesis of O-methylcorytenchirine

“…15 The radical precursor 24 was readily prepared from 4-methoxypyridine by treatment with 2-bromophenylacetyl chloroformate and phenylmagnesium bromide following standard procedures. 16 However, syringe pump slow addition of tributylstannane to 24 in benzene or t-butylbenzene at 80°C or 110°C afforded only the directly reduced product 27. It is clear from these observations that the radical derived from 24 undergoes cyclization too slowly to compete effectively with hydrogen atom transfer from the stannane under the conditions employed to give 27.…”

Recent advances in the chemistry of azapyranose sugars

“…73 The reaction of 4-methoxy-3-(triisopropylsilyl)pyridine 64 74 67. Selective acetoxylation was achieved using Pb(OAc) 4 (acetate delivery from the axial direction of a chair like transition state) 74 to give dihydropyridone 68 in 74% yield. The acetate group was subsequently removed using 10% HCl in ethanol and reduction achieved with tetramethylammonium triacetoxyborohydride to give diol 69 stereoselectively.…”