Accessing Borazine Substitution Patterns through Late‐Stage Iodination

Abstract

We have defined a procedure for the late‐stage functionalization of aryl borazines to facilitate the synthesis of a diverse array of borazine derivatives with varying substitution patterns, paving the way for further exploration of the field. More in detail, we have studied and disclosed a simple iodination procedure that could be applied to several differently substituted substrates (1 a–i) with mostly good to excellent yields (47–96%). The representative iodinated compounds 2 b and 2 e, were utilized to test their use in further representative functionalization steps such as cyanation, Heck, and Sonogashira reactions. All products 3 a–e were obtained in satisfactory good to very good yields considering the multiple (three or six times) concomitant reactions.

A waste-minimized approach for the synthesis of iodinated organic borazines

“…Initially, we developed a solution-based iodination approach adapted from literature procedures 23 using silver salts as mild and selective oxidants in combination with iodine. 24 This reaction was found to work in high yields and selectivity, however, the use of silver salts (featuring a toxic and ecotoxic heavy metal), 25,26 and large amounts of non-recoverable halogenated solvents are necessary, clearly posing some issues in terms of green chemistry.…”

“…We investigated this route by considering the conditions already developed for in-solution iodination (I 2 , AgNO 3 , DCM/MeCN) of borazine 2 . 24 Results reported in Table 1 have been obtained by partially or entirely removing the solvent and adopting ball-milling conditions.…”