On the regioselectivity of the reaction of N-methoxycarbonylpyridinium chloride with Grignard reagents: highly regioselective synthesis of 2-substituted N-methoxycarbonyl-1,2-dihydropyridines.

Insertion of Pyridine into the Calcium Allyl Bond: Regioselective 1,4‐Dihydropyridine Formation and CH Bond Activation

“…[15] The reaction energy profile for the proposed mechanism was studied by means of computational methods (Figure 1 The proposed mechanism is in agreement with results of NMR-scale reactions of 1 with two equiv of the methylated pyridine derivatives 2-, 3-, and 4-methylpyridine (5,7,8) and also 2,6-and 3,5-dimethylpyridine (6, 9; Scheme 3). The importance of vacant ortho and para positions for the insertion to occur is reflected by the metalation of CÀH bond activation products along with propene evolution, as observed with 2-picoline (5), 2,6-lutidine (6), and 4-picoline (7).…”

“…[2a, 4] Grignard [5] or organotin [6] reagents mainly add to give 2-substituted DHPs. 1,4-DHPs with substituents in the 4-position can be obtained with ill-defined organotitanium reagents, [7] lithium dialkylcuprates, [8] and mixtures of Grignard reagents or zinc organyls with cuprous salts.…”

Efficient Solution‐Phase Parallel Synthesis of 4‐Substituted N‐Protected Piperidines

“…[8,9] A wide range of organometallic reagents have also been used as nucleophiles in these reactions. Uncatalyzed Grignard [10] and organotin [11] reagents favor the formation of 2-substituted dihydropyridines, whereas the use of organotitanium reagents [12,13] and lithium dialkylcuprates [14] mainly results in 4-substituted dihydropyridines, which is also the case for Grignard reagents admixed with copper iodide. [15] Organozinc reagents are reported to give mainly mixtures of 4-and 2-substituted dihydropyridines.…”

Enzymatically Asymmetrised Chiral Building Blocks for the Synthesis of Complex Natural Product Analogues: The Synthesis of Dynemicin Analogues from 2‐(Quinolin‐4‐yl)propane‐1,3‐diol

“…[39] The monoacetate (S)-18 was converted into the three orthogonally diprotected 2-(quinolin-4-yl)-propane-1,3-diols 19-21 (Scheme 3). In a previous work [40] we had already described the yields and diastereoselectivities of protecting-group-controlled Yamaguchi [41,42] additions of magnesium trimethylsilylacetylide to these derivatives. The best results were obtained with compound 19, containing the triphenylmethyl (Tr) and acetyl groups, which gave a 94 % yield with a 70:30 diastereomeric ratio.…”