Regioselective homolytic substitution of benzo[c][2,7]naphthyridines

Cyanoquinolines and Furo[3,4-b]quinolinones Formation via On-The-Spot 2,3-Functionalization of Quinolines with Cyanopropargylic Alcohols

A convenient approach to 2-(1-ethoxyalkoxy)-3-cyanoquinolines (in up to 50% yields) has been developed. The approach comprises functionalization of quinolines with acetals of cyanopropargylic alcohols (KOH/H₂O/MeCN, 55-60 °C) followed by their transformation to furo[3,4-b]quinolinones (in up to 98% yields) via the sequential removal of acetal protection and intramolecular cyclization/hydration (7% aqueous HCl, acetone, 20-25 °C).

Electrochemical Properties and Excited-State Dynamics of Azaperylene Derivatives

A series of azaperylene derivatives such as monoazaperylene (MAPery), 1,6-diazaperylene (1,6-DiAPery), 1,7-diazaperylene (1,7-DiAPery), 1,12-diazaperylene (1,12-DiAPery), triazaperylene (TriAPery), and tetraazaperylene (TetAPery) was synthesized by changing the position and number of nitrogen atoms at the bay region of a perylene skeleton in 1, 6, 7, and 12 positions. The density functional theory (DFT) calculations and electrochemical measurements suggested that the energies of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) states significantly become stabilized with increasing the number of nitrogen atoms, whereas the estimated HOMO-LUMO gaps approximately remain constant. This result is in good agreement with the absorption and fluorescence spectral measurements. Additionally, these steady-state spectroscopic measurements demonstrate the broadened spectra as compared to pristine perylene (Pery). In photophysical measurements, the fluorescence quantum yields (Φ_FL) significantly decreased as the number of nitrogen atoms increased, whereas much enhanced quantum yields and rate constants of internal conversion (Φ_IC and k_IC) were observed. Especially, the increased k_IC values of TriAPery (k_IC: ∼10⁸ s^-1) and TetAPery (k_IC: ∼10⁹ s^-1) are much larger than those of diazaperylene and monoazaperylene derivatives (k_IC: ∼10⁷ s^-1). These photophysical trends were successfully explained by time-dependent DFT (TD-DFT) calculations. Finally, the characteristic protonated and deprotonated processes of nitrogen atoms in azaperylenes under acidic conditions were monitored utilizing absorption and fluorescence measurements. The binding constants demonstrate that the nitrogen atoms at 1 and 12 positions of a perylene skeleton are essential for the increased values.

Novel 1,8-Naphthyridine Derivatives: Design, Synthesis and in vitro screening of their cytotoxic activity against MCF7 cell line

A series of new 2-phenyl-7-methyl-1,8-naphthyridine derivatives with variable substituents at C3 were synthesized for an in vitro evaluation of their anticancer activity against human breast cancer cell line (MCF7). On one hand, compounds 3f, 6f, 8c, and 10b showed IC50 values (6.53, 7.88, 7.89, 7.79 μM, respectively) compared to that of the mentioned drug staurosparine (IC50 = 4.51 μM). On the other hand, derivatives 10c, 8d, 4d, 10f and 8b displayed better activity than staurosporin with IC50 values (1.47, 1.62, 1.68, 2.30, 3.19 μM, respectively).

Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

Readily available 4-bromobenzo[c][2,7]naphthyridine undergoes regioselective direct ring metalation at C-5 with TMPMgCl∙LiCl at −40 °C. Quenching with various electrophiles gives a broad range of 5-substituted products, which are building blocks for the synthesis of heterocyclic natural products and analogues thereof. In combination with a Parham-type cyclization a novel approach to pyrido[4,3,2-mn]acridones has been worked out.

Rhodium(II)-Catalyzed Annulation of Azavinyl Carbenes Through Ring-Expansion of 1,3,5-Trioxane: Rapid Access to Nine-Membered 1,3,5,7-Trioxazonines

The rhodium(II)-catalyzed denitrogenative coupling of N-alkylsulfonyl 1,2,3-triazoles with 1,3,5-trioxane led to nine-membered-ringed trioxazonines in moderate-to-good yields. 1,3,5-Trioxane, acting as an oxygen nucleophile, reacted with the α-aza-vinylcarbene intermediate, giving rise to ylide formation, which was probably the key step in the reaction. Triazoles that contained aryl substituents with various electronic and steric features on the C4 carbon atom were well-tolerated. The synthesis of trioxazonine derivatives was achieved through a one-pot, two-step procedure from 1-mesylazide and a terminal alkyne by combining Cu(I)-catalyzed 1,3-dipolar cycloaddition and rhodium-catalyzed transformations.

A novel approach to the pyridoacridine ring system: synthesis of the topoisomerase inhibitor 13-deazaascididemin

A novel approach to the pyridoacridine ring system of the ascididemin-type marine alkaloids is presented. This approach allows for the introduction of the ring A of the alkaloids by using a simple aromatic aldehyde building block. The viability of this approach is demonstrated with the synthesis of AK37, a bioactive deaza analogue of the alkaloid ascididemin. Starting from 3-cyano-4-methylquinoline, a sequence of regioselective homolytic benzoylation, annulation of a bromopyridine ring, and radical cyclization leads to the pentacyclic ring system.