Reaction of 2-trifluoroacetyl-1,8-Bis(dimethylamino)naphthalene with strong organic bases: Deprotonation of 1-NMe 2 group resulting in the formation of Benzo[g]indole derivatives versus nucleophilic addition to C O group

"Buttressing Effect" in the Halogen-Lithium Exchange in ortho-Bromo-N,N-dimethylanilines and Related Naphthalenes

Non-covalent interactions such as coordination of an organolithium reagent by a directing group and steric repulsion of substituents strongly affect the halogen-lithium exchange process. Here we present the manifestation of the "buttressing effect" - an indirect interaction between two substituents issued by the presence of a third group - and its influence on the ease and selectivity of the bromine-lithium exchange and the reactivity of formed aryllithiums. The increase of the size of the "buttressing" substituent strongly affects the conformation of a NMe2 group, forcing it to hinder ortho-bromine and thus slowing down the exchange. In naphthalene substrates bearing two bromines, this suppresses regioselectivity of the reaction. The "buttressing effect" forces formed aryllithiums to deaggregate, thus boosting their reactivity. This facilitates the decomposition via protolisys by ethereal solvents even at low temperatures and in some cases initiates fast Wurtz-Fittig coupling.

Transition-Metal-Free Synthesis of 2-Substituted Benzo[cd]Indoles via the Reaction of 1-Halo-8-lithionaphthalenes with Nitriles

A simple and effective organolithium approach to the synthesis of 2-substituted benzo[cd]indoles from peri-dihalonaphthalenes and nitriles has been developed. The reaction proceeds via a surprisingly easy intramolecular aromatic nucleophilic substitution facilitated by the "clothespin effect". The discovered transformation provides good isolated yields, allows usage of an extensive range of nitriles, and demonstrates a good substituents tolerance. UV-absorption and NMR spectra of the obtained benzo[cd]indoles and their protonated forms demonstrated exclusive protonation to the indole nitrogen atom even in the presence of two NMe2 groups in positions 5 and 6 (i. e. "proton sponge" moiety).

Choice of computational protocol for carbon-lithium spin-spin coupling constants 1 JCLi

In this work, we tested various computational schemes for calculations of ¹ J_CLi constants with a high accuracy. On the example of six organolithium reagents (phenyllithium monomer and dimer, monomer s-butyllithium, monomers of 1- and 2-lithionaphthalenes, and a methyllithium tetramer), the following aspects are discussed: (i) the role of a model system geometry, (ii) influence of solvent effects, and (iii) the choice of a functional and basis set. Practical recommendations for calculation of ¹ J_CLi with an accuracy ±2 Hz are formulated.

Sterically Facilitated Intramolecular Nucleophilic NMe2 Group Substitution in the Synthesis of Fused Isoxazoles: Theoretical Study

The influence of steric repulsion between the NMe₂ group and a second ortho-(peri-)substituent in the series of 1-dimethylaminonaphthalene and N,N-dimethylanilene ortho-oximes on the ease of the NMe₂ group’s intramolecular nucleophilic substitution is studied. Possible reaction intermediates for three mechanisms are calculated (ωB97xd/def-2-TZVP), and their free Gibbs energies are compared to model reaction profiles. Supporting experiments have proved the absence of studied reactivity in the case of simple 2-dimethylaminobenzaldoxime, which allowed us to establish reactivity limits. The significant facilitation of NMe₂ group displacement in the presence of bulky substituents is demonstrated. The possibility of fused isoxazoles synthesis via the intramolecular nucleophilic substitution of a protonated NMe₂ group in the aniline and naphthalene series is predicted.

Synthesis of CF3CH2-Containing Indolines by Transition-Metal-Free Aryltrifluoromethylation of Unactivated Alkenes

With an unactivated double bond as the radical acceptor, allyl amines underwent a metal-free trifluoromethylation/cyclization cascade with CF₃SO₂Na (Langlois' reagent), affording CF₃CH₂-containing indolines and tetrahydroisoquinolines, whose practical syntheses are significant challenges. This protocol features mild conditions, low cost, and a broad substrate scope.