Regioselective Diversification of 2,1-Borazaronaphthalenes: Unlocking Isosteric Space via C-H Activation.

Methods for the regioselective C-H borylation and subsequent cross-coupling of the 2,1-borazaronaphthalene core are reported. Azaborines are dependent on B-N/C═C isosterism when employed in strategies for developing diverse heterocyclic scaffolds. Although 2,1-borazaronaphthalene is closely related to naphthalene in terms of structure, the argument is made that the former has electronic similarities to indole. Based on that premise, iridium-mediated C-H activation has enabled facile installation of a versatile, nucleophilic coupling handle at a previously inaccessible site of 2,1-borazaronaphthalenes. A variety of substituted 2,1-borazaronaphthalene cores can be successfully borylated and further cross-coupled in a facile manner to yield diverse C(8)-substituted 2,1-borazaronaphthalenes.

Azaborininones: Synthesis and Structural Analysis of a Carbonyl-Containing Class of Azaborines.

An approach to access azaborininones (carbonyl-containing, boron-based heterocyclic scaffolds) using simple reagents and conditions from both organotrifluoroborates and boronic acids is described. An inexpensive, common reagent, SiO2, was found to serve as both a fluorophile and desiccant to facilitate the annulation process across three different azaborininone platforms. Computational analysis of some of the cores synthesized in this study was undertaken to compare the azaborininones with the analogous carbon-based heterocyclic systems. Computationally derived pKa values, NICS aromaticity calculations, and electrostatic potential surfaces revealed a unique isoelectronic/isostructural relationship between these azaborines and their carbon isosteres that changed based on boron connectivity. Correlation to experimentally derived data supports the computational findings.

One-pot synthesis and sigma receptor binding studies of novel spirocyclic-2,6-diketopiperazine derivatives.

New spirocyclic-2,6-diketopiperazine derivatives containing benzylpiperidine and cycloalkane moieties were synthesized by a one-pot two-step sequential Ugi/intramolecular N-amidation process in moderate to good yields. The in vitro ligand-binding profile studies performed on the sigma-1 and sigma-2 receptors revealed that the σ1 affinities and subtype selectivities of three spirocyclic piperidine derivatives are generally comparable to those of spirocycloalkane analogues. Compared to the low σ1 affinities obtained for cycloalkyl-substituted spirocyclic-2,6-diketopiperazines with n=2, those with n=1 proved to have optimal fitting with σ2 subtype by exhibiting higher affinities. Moreover, the best binding affinity and subtype selectivity was identified for compound 3c with Kiσ1=5.9±0.5nM and Kiσ2=563±21nM as well as 95-fold σ1/σ2 selectivity ratio, respectively.

Synthesis of diheterocyclic compounds based on triazolyl methoxy phenylquinazolines via a one-pot four-component-click reaction.

A facile and highly efficient method for one-pot four-component synthesis of triazolyl methoxy phenylquinazolines is described. A mixture of aromatic propargylated aldehydes, different azides, 2-aminobenzophenone derivatives, and ammonium acetate were condensed in the presence of catalytic amounts of acidic ionic liquid, 1-methylimidazolium trifluoroacetate, ([Hmim]TFA), and Cu(OAc)(2)/sodium ascorbate to afford the corresponding products in excellent yields. This methodology is highly efficient for structurally diverse azides.