Interaction of 1,3,2,4-benzodithiadiazines with aromatic phosphines and phosphites

Although an interaction between hydrocarbon and fluorocarbon 1,3,2,4-benzodithiadiazines (1 ) and P(C6H5)3 continuously produces chiral 1,2,3-benzodithiadiazol-2-yl iminophosporanes (2; in this work, 5,7-difluoro derivative 2a ) via 1:1 condensation, an interaction between 1 and other PR3 reagents gives different products. With R [DOUBLE BOND] OC6H5 and both hydrocarbon and fluorocarbon 1, only X=P(OC6H5)3 (X = S, O) were identified in the complex reaction mixtures by 13С and 31Р NMR and GC-MS. With R = C6F5, no interaction with the archetypal 1 was observed but catalytic addition of atmospheric water to the heterocycle afforded 2-amino-N-sulfinylbenzenesulfenamide (4 ). With electrophilic B(C6F5)3 instead of nucleophilic P(C6F5)3, only adduct H3N→B(C6F5)3 and a new polymorph of C6F5B(OH)2 were isolated and identified by X-ray diffraction (XRD). A molecular structure of 2a was confirmed by XRD, and the π-stacked orientation of one of phenyl groups and heterocyclic moiety was observed. This structure is in general agreement with that calculated at the RI-MP2 level of theory, as well as at three different levels of DFT theory with the PBE and B3LYP functionals. Mild thermolysis of 2a in a dilute decane solution gave persistent 5,7-difluoro-1,2,3-benzodithiazolyl (3a ) identified by EPR in combination with DFT calculations

Interaction of 1,3,2,4-benzodithiadiazines with aromatic phosphines and phosphites

Although an interaction between hydrocarbon and fluorocarbon 1,3,2,4-benzodithiadiazines (1 ) and P(C6H5)3 continuously produces chiral 1,2,3-benzodithiadiazol-2-yl iminophosporanes (2; in this work, 5,7-difluoro derivative 2a ) via 1:1 condensation, an interaction between 1 and other PR3 reagents gives different products. With R [DOUBLE BOND] OC6H5 and both hydrocarbon and fluorocarbon 1, only X=P(OC6H5)3 (X = S, O) were identified in the complex reaction mixtures by 13С and 31Р NMR and GC-MS. With R = C6F5, no interaction with the archetypal 1 was observed but catalytic addition of atmospheric water to the heterocycle afforded 2-amino-N-sulfinylbenzenesulfenamide (4 ). With electrophilic B(C6F5)3 instead of nucleophilic P(C6F5)3, only adduct H3N→B(C6F5)3 and a new polymorph of C6F5B(OH)2 were isolated and identified by X-ray diffraction (XRD). A molecular structure of 2a was confirmed by XRD, and the π-stacked orientation of one of phenyl groups and heterocyclic moiety was observed. This structure is in general agreement with that calculated at the RI-MP2 level of theory, as well as at three different levels of DFT theory with the PBE and B3LYP functionals. Mild thermolysis of 2a in a dilute decane solution gave persistent 5,7-difluoro-1,2,3-benzodithiazolyl (3a ) identified by EPR in combination with DFT calculations

Human Serum Albumin Labelled with Sterically-Hindered Nitroxides as Potential MRI Contrast Agents

Four albumin-nitroxide conjugates were prepared and tested as metal-free organic radical contrast agents (ORCAs) for magnetic resonance imaging (MRI). Each human serum albumin (HSA) carrier bears multiple nitroxides conjugated via homocysteine thiolactones. These molecular conjugates retain important physical and biological properties of their HSA component, and the resistance of their nitroxide groups to bioreduction was retained or enhanced. The relaxivities are similar for these four conjugates and are much greater than those of their individual components: the HSA or the small nitroxide molecules. This new family of conjugates has excellent prospects for optimization as ORCA