Confirmation of Microwave-Assisted Synthesis of Chloro-Boron Subphthalocyanines and Chloro-Boron Subnaphthalocyanines with Rapid Screening and Data Acquisition via HPLC-PDA

Herein, we report an investigation into the use of a scientific microwave reactor for the synthesis of chloro-boron subphthalocyanines (Cl-BsubPcs), its derivatives, and the π-extended alternative called chloro-boron subnaphthalocyanine (Cl-Cl _n BsubNc). Reaction optimization screening is presented with the aid of a high-pressure liquid chromatography system equipped with a photodiode array detector (HPLC-PDA) and used for quantitative analysis to calculate the conversion of phthalonitriles and 2,3-dicyanonaphthalene to the Cl-BsubPcs and Cl-Cl _n BsubNcs, respectively, by leveraging the characteristic UV-vis absorbance profiles of the Cl-BsubPcs and Cl-Cl _n BsubNcs. The microwave reaction process was found to reduce the reaction time from multiple hours to 5 to 36 min, reducing the overall time needed for the synthesis of the desired compounds, and provided a streamlined process of optimizing the synthesis of peripherally and axially substituted Cl-BsubPc derivatives. With enhanced heating, difficult-to-synthesize Cl-Cl₁₂BsubPc was found to achieve moderate conversion through multiple microwave irradiation cycles. With this streamlined process, the lack of ethereal cleavage of aryl-aryl ether moieties (i.e., p-tolyl group) attached to the periphery of a Cl-BsubPc was achieved and is also presented. Although random bay halogenation of Cl-BsubNc was not found to be suppressed under the reaction conditions in the microwave, we present the microwave synthesis of Cl-Cl _n BsubNcs while tracking random bay halogenation production using HPLC-PDA and confirm their characterization via mass spectrometry.