Phosphazenes reactions with ketones

Further reactions of P-hydridocyclotriphosphazenes (See Section IV,E) have been described. They undergo insertion reactions with aldehydes, ketones, isothiocyanates and electrophilic olefins. Addition of sulfur or oxidation with KMn04 gives thioxo-or oxo-cyclotriphos-phazene derivatives which are methylated at the chalcogen to afford methylthio- and methoxy- cyclotriphosphazenes (36). Hydridocyclo-phosphazenes can also be oxidized to give symmetric and unsymmetric bis(cyclotriphosphazenyl) oxides (35). 

Reactions of phosphazenes (22) and (23) with aldehydes, ketones and nitriles provide a convenient route to new heterocycles containing l,3-oxaza-4-phospha-2-phosphorine (24) and l,3-diaza-4-phospha-2-phosphorine (25) rings respectively (Scheme 3) ... 

Numerous reactions, involving either transformation or conservation of the phosphazene unit, have been reported. The oxidation of the indanone phosphazene, 12, with singlet oxygen yields the corresponding ketone and triphenylphosphine oxide presumably via... 

Chlorocyclophosphazenes react with organic acids or their salts (21, 346, 448), acid amides (206), and acid halides (207) to yield the nitrile of the acid the phosphazene ring is degraded. The reaction of benzoyl chloride with [NP(OEt)2]3 4 gives ethyl chloride, ethyl phos-phenates, and triphenyl-s-triazine (188). The trifluoroethoxy derivatives, [NP(OCH2CF3)2]3 4, react with diphenyl ketone to afford the acid, (CF3CH20)2P(0)(0H), and organic imines (405, 406). 

The reactions of amino-phosphites with activated olefins, and with activated ketones, provide a route to phosphazenes (31) and (32), respectively. 

As already described, the C3 and C4 functionalization of pyridazine rely on highly reactive metallic bases (e.g., alkyl lithium). However, a nonmetallic phosphazene base (f-Bu-P4) can be used in place of lithium 2,2,6,6-tetramethylpiperidinide, for the addition of ketones to pyridazine. When benzophenone is reacted with pyridazine in toluene, the method is highly Cq-regioselective and efficient—91% yield (eq 10). In addition to the phosphazene base, zinc iodide (1 equiv) is also added to the reaction mixture. Its role is not yet well understood, but it is critical to formation of the product (4% yield without zinc iodide). 

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