The unusual 1,4-chelation-controlled nucleophilic addition to aldehydes with high stereoselectivity. A systematic study of stereoselectivity in the addition reaction of carbon nucleophiles to cis-substituted cyclopropanecarbaldehydes

Stable isotope synthesis of glycine transporter 1 inhibitor Iclepertin (BI 425809) and its major metabolites

Stable isotope labeled Iclepertin (BI 425809, 1) and its major metabolites are needed as internal standards in bioanalytical studies. BI 425809 consists of two main building blocks, 5-methylsulfonyl-2-[(1R)-2,2,2-trifluoro-1-methyl-ethoxy]benzoic acid (2) and 3-[(1R,5R)-3-azabicyclo[3.1.0]hexan-5-yl]-5-(trifluoromethyl)isoxazole (3) linked to each other via an amide bond. We used fluoro[13 C6 ]benzene as the starting material in the preparation of [13 C6 ]-2. This intermediate was then employed to access carbon 13 labeled Iclepertin ([13 C6 ]-1) and other metabolites. The major metabolite BI 761036 (6), which resulted from cytochrome P450 oxidation and amide hydrolysis of BI 425809, was prepared labeled with carbon 13 and nitrogen 15 via two synthetic routes. In the first route, diethyl [13 C3 ]malonate, [13 C]methyl iodide, and hydroxyl[15 N]amine were used to provide [13 C4 ,15 N]-BI 761036 ([13 C4 ,15 N]-6a) in 13 steps in 6% overall yield, whereas in the second route, [13 C3 ]propargyl alcohol, potassium [13 C]cyanide, and [15 N]ammonia were used to furnish [13 C4 ,15 N]-BI 761036 ([13 C4 ,15 N]-6b) in 11 steps in 1% overall yield. The detailed stable isotope synthesis of 1 and its major metabolites is described.

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin-Anh and Chelation-Control Models

This review describes the additions of allylmagnesium reagents to carbonyl compounds and to imines, focusing on the differences in reactivity between allylmagnesium halides and other Grignard reagents. In many cases, allylmagnesium reagents either react with low stereoselectivity when other Grignard reagents react with high selectivity, or allylmagnesium reagents react with the opposite stereoselectivity. This review collects hundreds of examples, discusses the origins of stereoselectivities or the lack of stereoselectivity, and evaluates why selectivity may not occur and when it will likely occur.

Synthesis of Chiral cis-Cyclopropane Bearing Indole and Chromone as Potential TNFα Inhibitors

Conformationally restricted analogues of SPD-304, the first small-molecule TNFα inhibitor, in which two heteroaryl groups, indole and chromone, are connected by chiral methyl- or ethyl- cis-cyclopropane, were designed. Synthesis of these molecules was achieved via Suzuki-Miyaura or Stille coupling reactions with chiral bromomethylenecyclopropane or iodovinyl- cis-cyclopropane as the substrate, both of which were prepared from chiral methylenecyclopropane as a common intermediate, constructing the heteroaryl-methyl or -ethyl- cis-cyclopropane structures as key steps. This study presents an efficient synthesis of a series of chiral cis-cyclopropane conjugates with two heteroaryl groups.

Selectivity in the addition reactions of organometallic reagents to aziridine-2-carboxaldehydes: the effects of protecting groups and substitution patterns

Good to excellent stereoselectivity has been found in the addition reactions of Grignard and organozinc reagents to N-protected aziridine-2-carboxaldehydes. Specifically, high syn selectivity was obtained with benzyl-protected cis, tert-butyloxycarbonyl-protected trans, and tosyl-protected 2,3-disubstituted aziridine-2-carboxaldehydes. Furthermore, rate and selectivity effects of ring substituents, temperature, solvent, and Lewis acid and base modifiers were studied. The diastereomeric preference of addition is dominated by the substrate aziridines' substitution pattern and especially the electronic character and conformational preferences of the nitrogen protecting groups. To help rationalize the observed stereochemical outcomes, conformational and electronic structural analyses of a series of model systems representing the various substitution patterns have been explored by density functional calculations at the B3LYP/6-31G* level of theory with the SM8 solvation model to account for solvent effects.

Highly Stereoselective Grignard Addition to Cis-Substituted C-Cyclopropylaldonitrones. The Bisected s-Trans Transition State Can Be Stabilized Effectively by the Lewis Acid-Coordination

We previously found that Grignard addition to a C-cyclopropylaldonitrone, C-[cis-2-(N,N-diethylcarbamoyl)-trans-2-phenylcyclopropyl]-N-benzylaldonitrone (1), stereoselectively gave the anti-product 3, in which the stereoselectivity was particularly high when MgBr(2) was the additive. In this study, the reaction pathway was investigated in detail. The stereoselective addition was initially thought to occur via either a 1,5-chelation-controlled or a bisected s-trans conformation-controlled pathway. However, Grignard addition to a nonchelating silyl ether-type substrate, C-[cis-2-(tert-butyldiphenylsilyloxymethyl)-trans-2-phenylcyclopropyl]-N-benzylaldonitrone (7), also gave the anti-product 9 with high stereoselectivity suggesting that chelation is not important in the reaction. Theoretical calculations of C-cyclopropylaldonitrones showed that the coordination of Mg(2+) at the nitrone oxygen significantly stabilizes the bisected s-trans conformer due to the effective hyperconjugation between the pi* of the nitrone C=N bond and the electron-donating cyclopropane orbitals. This kind of orbital interaction is able to stabilize the transition state of the nucleophilic addition and is maximized in the bisected conformation, in which the orbitals of the forming bond and the cyclopropane C-C bond are in an almost planar arrangement. Thus, the high stereoselectivity can be explained by nucleophilic attack on the less hindered side of the C=N bond of the substrates in the Mg(2+)-coordinated bisected s-trans conformation.