Reactivity of cyclic arsenites and phosphites: X-ray structures of bis(5,5-dimethyl-1,3,2-dioxarsenan-2-yl) ether and bis(2,4,8,10-tetra-terf- butyl-12H-dibenzo [d,g] [1,3,2]dioxarsenocin-6-yl) ether

Abstract

Reaction of the chlorophosphite ClPOCH2CMe2CH 2O 1 with cyclohexylamine gave the expected product (C 6H11NH)POCH2CMe2CH2O 3 whereas the corresponding chloroarsenite 2 led to the bridged compound 12. When the reaction was performed in the presence of water, 1 gave the expected product H(O)POCH2CMe2CH2O 11 whereas 2 gave the oxo-bridged compound (AsOCH2CMe2CH2O) 2O 13. The amino phosphite 3 underwent hydrolysis to afford the ring cleaved product 18 whereas the phenoxy phosphite 21 led to the ring preserved compound 11. In contrast, the corresponding phenoxy arsenite (PhO)AsOCH 2CMe2CH2O 25 gave the oxo-bridged compound 13. Addition of perchloro-o-benzoquinone to the phosphite 23 was highly exothermic and afforded the phosphorane 29; however the corresponding arsenonate 27 reacted very sluggishly at room temperature and when heated gave an uncharacterizable mixture of products. The identity of the title oxy-bridged compounds 13 and 15 obtained here has been confirmed by X-ray structure determination; the six-membered rings in 13 have a 'chair' conformation and the eight-membered rings in 15 have a 'symmetrical anti' conformation.