Synthesis of Tricyclic (λ5)‐Phosphoranes; unusual N‐demethylation/N‐alkylation reactions during the oxidative addition of hexafluoroacetone and tetrachloro‐ortho‐benzoquinone to benzodiaza‐λ3‐phosphorinones. Single crystal X‐ray diffraction studies of various products

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AbstractThe reaction of methylisatoic acid anhydride 1 with benzylamines led to the N‐benzyl‐N′‐methylanthranilamide derivatives 2 – 4. Their reaction with phosphorus trichloride furnished the 2‐chloro‐1‐halobenzyl/benzyl‐3‐methyl‐4(1 H)‐1,3,2‐benzodiazaphosphorin‐4‐ones 5 – 7 which, upon reaction with bis‐(2‐chloroethyl)ammonium chloride/triethylamine, were converted into the P‐bis‐(2‐chloroethyl)amino‐1‐halobenzyl/benzyl‐3‐methyl‐4(1 H)‐1,3,2‐benzodiazaphosphorin‐4‐ones 8 – 10 and 12. With 2‐chloroethylammonium chloride/triethyl‐amine the PNHCH2CH2Cl‐substituted compound 11 was obtained from the PIIICl‐species 6. The reaction of 8 – 10 and 12 with hexafluoroacetone (HFA) took an unusual course: apart from the oxidative addition of HFA and formation of the perfluoropinacolyl ring system, one of the two CH2CH2Cl groups was found to alkylate the CH3N atom with formation of a five‐membered (diazaphospholane) ring in the tricyclic phosphoranes 13 – 16. The reaction of 11 with HFA also produced a spirophosphorane 17 which involved a λ5‐oxazaphosphetidine ring system. In the reaction of 8, 10 and 12 with tetrachloro‐o‐benzoquinone, an oxidative addition reaction with concomitant N‐alkylation and formation of the tricyclic phosphoranes 18 – 20 was found to take place.Single crystal X‐ray structure determinations are described for the phosphoranes 13, 14 and 16, and for the precursor compound 9. The following features are common to the isostructural compounds 13 and 16 and the diethyl ether hemisolvate of 14: the (λ5)‐spiro phosphorus atom lies out of the plane of the other atoms of the rings to which it is common, and the dioxaphospholane rings display a twist conformation. In the λ3P‐compound 9 the phosphorus atom also lies out of the plane of the other ring atoms.