Efficient Synthesis of Bis(dibromomethyl)arenes as Important Precursors of Synthetically Useful Dialdehydes

Abstract

This work presents an efficient synthesis of bis(dibromomethyl)benzenes and a bis(dibromomethyl)thiophene as precursors of aromatic dialdehydes by bromination of dimethyl-substituted arenes under various reaction conditions (yields up to 99%). Several new variants of this reaction, including the use of N-bromosuccinimide (NBS) and bromine, and various solvents to replace carbon tetrachloride, benzene and carbon disulfide, were also tested. In the optimised protocols, the inconvenient solvents were replaced by 1,2-dichloroethane (DCE) and/or acetonitrile. In the DCE protocols, we reduced reaction times 24-32-fold, reduced the amount of NBS a fewfold and lowered power consumption relative to the literature protocols. The procedures also allowed elimination of long-lasting incandescent irradiation (100-500 W). The replacement of NBS by bromine led to a further reduction in the amount of brominating agent. The obtained bromo derivatives were efficiently converted into the corresponding dialdehydes (90-96%), which in turn are useful in materials chemistry.

Mono‐Aryl/Alkylthio‐Substituted (Hetero)acenes of Exceptional Thermal and Photochemical Stability by the Thio‐Friedel–Crafts/Bradsher Cyclization Reaction

“…We also explored an interesting approach to di‐aryl/alkylthio‐substituted pentacenes 14 by a double thio‐Friedel–Crafts/Bradsher cyclization of dithioethers 13 starting from 2,4‐dibromobenzene‐1,5‐dicarbaldehyde ( 7 ; Scheme ). Thus, acetalization of the dialdehyde 7 with 1,3‐propanediol afforded the corresponding diacetal 8 in an excellent yield of 99 %. Next, bis( trans ‐thioacetalization) of the latter with 1,3‐propanedithiol gave the bis(dithioacetal) 9 also in a yield of 99 % (Scheme ).…”

Latent Carbene: Diaminomethylation of Thiophenes

“…Both compounds are known in the literature. [10] Dialdehyde 13 was prepared previously via hydrolysis of polybrominated thiophene, [11] but it can be also obtained in a good yield via dilithiation of tetrabromothiophene followed by quenching with 1-formylpiperidine. [12,13] In our previous work, we investigated the reaction of silylformamidine 1 with 1,3-dihalobenzenes.…”

Enantioselective Synthesis of Dithia[5]helicenes and their Postsynthetic Functionalization to Access Dithia[9]helicenes

“…It is of note that methods for the transformation of helicoidal sulfones into other (hetero)helicene architectures are already known [8] . Additionally, treatment of rac‐ 7 a with an excess of N ‐bromosuccinimide (NBS) (3.0 equiv) resulted in the selective dibromination of both benzylic positions to deliver rac‐ 8 a through a Wohl–Ziegler reaction [20] …”