Hindered Spiro-Ketal Nitroxides

Spiro-ketal nitroxides have been prepared that are effective as regulators in nitroxide mediated polymerizations. These agents have high hydrocarbon and monomer solubility over existing nitroxides, particularly in styrene, and are also effective as regulators in vinyl acetate and acetonitrile polymerizations. 

A 500-ml Erlenmeyer flask was charged withl,5-dioxa-9-aza-8,8,10,10-tetramethyl-spiro [5,5]-undecane (0.04 mole) dissolved in 150 ml of methanol and then treated with 40 ml of 35% aqueous hydrogen peroxide followed by sodium tungstate dehydrate (0.4 g). The mixture was left for 3 days at ambient temperature where after one day the color became dark orange. It was then extracted with three 50-mI portions of t-butyl methyl ether and dried with an anhydrous Na2S04. The solution was concentrated, and 

9 g of a dark orange solid product was isolated, MP = 59-62°C. The use of this material and related nitroxide regulators in polymerization reactions are provided in Table 1. 

TABLE 1. Effectiveness of nitric oxide polymerization regulators on the polymerization of vinyl acetate and acetonitrile at 70°C using 10 ml of monomer, 0.35 g of benzoyl peroxide, and 0.1 g of selected nitroxide regulators. 

The Step 1 reagent l,5-dioxa-9-aza-8,8,10,10-tetramethylspiro[5,5]-undecane was prepared according to the method of Murayama [1]. 

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