Interaction of 1,3,2,4-Benzodithiadiazines and Their 1-Se Congeners with Ph3P and Some Properties of the Iminophosphorane Products
文摘
Interaction between Ph3P and 1,3,2,4-benzodithiadiazine (1); its 6,7-difluoro (2), 5,6,8-trifluoro (3) and 5,6,7,8-tetrafluoro (4) derivatives; and 5,6,8-trifluoro-3,1,2,4-benzothiaselenadiazine (5) proceeded via a 1:1 condensation to give Ph3P鈺怤鈭扲 iminophosphoranes (1a鈭?b>5a, R = corresponding 1,2,3-benzodichalcogenazol-2-yls), which are inaccessible by general approaches based on the Staudinger and Kirsanov reactions. In contrast, neither Ph3As nor Ph3Sb reacted with 1 and 4. Molecular structures of 1a鈭?b>5a and 5 were confirmed by X-ray diffraction (XRD). The crystals formed by chiral molecules of 2a鈭?b>5a were racemic, whereas the crystal of 1a was formed by a single enantiomer. In all of the Ph3P鈺怤鈭扲 derivatives, one of the Ph rings is oriented face-to-face to the hetero ring, R. Upon heating to 120 掳C in squalane (1a, 3a, 4a) or dissolving in chloroform at ambient temperatures (1a, 2a, 4a), the Ph3P鈺怤鈭扲 derivatives generated the 1,2,3-benzodithiazolyls (1b鈭?b>4b, respectively) whose identity was confirmed by electron paramagnetic resonance (EPR). 2,1,3-Benzothiaselenazolyls 5b and 6b were detected by EPR as the main paramagnetic products of solution thermolysis of 5 and its 5,6,7,8-tetrafluoro congener (6), respectively. Passing a chloroform solution of 4a through silica column unexpectedly gave 5-6-6-6 tetracyclic (9) and 6-10-6 tricyclic (10) sulfur鈭抧itrogen compounds, which were characterized by XRD.
