Synthesis of Terminal-Biradical Compounds Consisting of Two N-Oxyl Groups Connected with Conjugated π-Systems
The design and synthesis of molecular magnets are one of the current interests. Essentials are how to increase the spin density and to regulate the direction of the spins. For latter purpose, the radicals are attempted to be joined by π-electron systems to allow to interact each other. Poly-radical compounds connecting the radicals by aromatic structure are reported. However, the overlap with aromatic ring seems not efficient because of a steric repulsion. We planed to connect radicals by other type of rzsystem, e.g., acetylenic and vinylic moieties. Herein, we describe synthetic results on terminal-biradical compounds 1 containing two N-oxyl groups connected with conjugated π-systems (Scheme 1) by (1) addition of magnesium acetylide to 4-oxo-TEMPO derivatives 2 followed by dehydration (Route A). or (2) Pd-catalyzed cross-coupling between acetylene derivatives and vinyl triflate 4 derived from 2 (Route B).1 The vinyl triflate 4 was found to be a potent intermediate to synthesize a variety of biradical compounds 1.
KeywordsAromatic Structure Steric Repulsion Molecular Magnet Potent Intermediate Acetylene Derivative
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