Macromolecular polyyne-containing benzoxazines for cross-linked polymerization

A Mannich condensation of 2,4-di-tert-butylphenol, p-bromophenethylamine, and formaldehyde followed by a Sonogashira coupling of the resulting 3-(4-bromophenethyl)-6,8-di-tert-butyl-3,4-dihydro-2H-benz[1,3]oxazine (1-Br) with TMSCCH gave acetylenic benzoxazine 1-C2TMS which was a precursor for polyynic derivatives. Firstly, it was deprotected with K2CO3 in iPrOH/MeOH to give the terminal acetylene 1-C2H, which was subsequently dimerized to the symmetrical diyne 1-C4-1. Next, 1-C2H was transformed to 1-C4TMS via a Cadiot–Chodkiewicz coupling, and then 1-C4TMS was homocoupled with in situ deprotection to give octatetrayne 1-C8-1. X-ray diffraction studies of 1-C8-1 showed distinctive chain bending and a packing analysis revealed the potential for 1,n-topochemical polymerization that implies a cross-linking opportunity.