One-Pot Synthesis of Brightly Fluorescent Mes₂B-Functionalized Indolizine Derivatives via Cycloaddition Reactions

Abstract

Four new BMes2-functionalized indolizine derivatives (Mes = mesityl) have been prepared via the cycloaddition reaction between pyrido[2,1-a]isoindole (A) or pyrrolo[1,2-a]pyridine (B) and BMes2-containing alkynes. All four compounds are brightly blue or blue-green fluorescent with λ(em) = 428-495 nm and Φ = 0.27-0.68, depending on the substitution position of the BMes2 group. Experimental and TD-DFT computational data indicated that the primary electronic transitions responsible for the fluorescence of 1-4 are from HOMO to LUMO (π → π*) rather than charge transfer from N → B, which is in agreement with previous findings suggesting that the lone-pair on N is delocalized throughout the N-heterocycles.

The opposite and amplifying effect of B ← N coordination on photophysical properties of regioisomers with an unsymmetrical backbone

“…1,3-Dipolar cycloaddition reactions of pyrido[2,1- a ]isoindole9 with internal alkynes decorated by BMes 2 ph and N-aromatic units were employed to synthesize the 5 pairs of regioisomers using the general one-pot, two-step procedure shown in Scheme 2. Previously, terminal alkynes containing a BMes 2 Ph unit were investigated for this type of reaction, which led to the exclusive formation of species that have the boron unit at the C1 position 3 b .…”

“…The IDI molecule is an electron-rich substrate. BMes 2 Ph and py attached to IDI are mainly inductively EDG and EWG, respectively 9. As shown in Scheme 1b, the C1 and C2 atoms in IDI have the highest and the lowest electron density, respectively, among the carbon atoms (electrostatic potential charge = –0.421 for C1, –0.110 for C2).…”

Moderne Strategien zur Synthese funktioneller Fluorophore

“…L‐förmige Penta‐, Hexa‐ und Heptacyclen mit einer Pyrrolo[1,2‐ a ][1,8]naphthyridin‐Einheit wurden als Fluorophore mit blauer bis orangefarbener Emission in einem Eintopfprozess hergestellt. Alkine wurden auch mit Pyridoisoindolen und Pyrrolopyridinen umgesetzt, um Indolizine durch intermoleklare thermale Cycloaddition und DDQ‐gestützte Oxidation herzustellen (DDQ=2,3‐Dichlor‐5,6‐dicyan‐1,4‐benzochinon) …”

Enantioselective Construction of the Cycl[3.2.2]azine Core via Organocatalytic [12 + 2] Cycloadditions

“…Specifically, the cycl[3.2.2]­azine core (pyrrolo­[2,1,5- cd ]­indolizine, Figure ) has been found in the natural product vlasoulamine A, as well as in a variety of saturated compounds belonging to the family of myrmicarins (see, e.g., myrmicarin 215A) . Several unsaturated cycl[3.2.2]­azine derivatives, such as NNC 45–0095, have displayed high activity as nonsteroidal agonists for the estrogen receptor through mimicking the steroid core with their tricyclic nucleus. , In addition to these biological prospects, related benzo­[ a ]­cycl­[3.2.2]­azines (indolizino­[3,4,5- ab ]­isoindoles) have drawn interest as potent organic fluorophores. , The latter examples all feature one 5-membered ring which is disubstituted, extending the conjugation.…”

“…17,18 In addition to these biological prospects, related benzo[a]cycl[3.2.2]azines (indolizino [3,4,5-ab]isoindoles) have drawn interest as potent organic fluorophores. 19,20 The latter examples all feature one 5-membered ring which is disubstituted, extending the conjugation. The cycl[3.2.2]azine core has historically been accessed through annulation of substituted indolizines, as illustrated by Boekelheide, 13 or that of 3H-pyrrolizine has been accessed with vinamidinium salts.…”