Synthesis of novel functional styrene monomers having trimethylsilyl and hydroxyalkyl groups by the reaction between 4‐vinylbenzyllithium derivatives and oxiranes

Abstract

New synthetic routes for styrene derivatives having both trimethylsilyl and hydroxyalkyl groups were investigated. Reactions between oxirane (Sa) and chemical s p i e s present in an equilibrium system resulting from 4-(trimethylsilylmethyl)styrene (1 s) and lithium diisopropylamide (2) in tetrahydrofuran give an addition product 8 a ) between 2 and Sa preferentially. By using alkylsubstituted oxiranes such as ethyloxirane (5e) and tert-butyloxirane (Se), a i : 1 addition reaction of 1s with the oxiranes takes place predominantly to form i-alkyl-3-trimethylsilyl-3-pVinylphenyl-I-propanol(8) homologues. From results of studies on the reaction between 2 and several oxiranes, it was concluded that the selective formation of 8 homologues was attained by suppression of reactions between oxirane and 2 owing to steric hindrance between alkyl substituents of oximne and isopropyl groups of 2. The reactivity of 8 in polymerization reaction was also estimated on the basis of spectroscopic measurements. 8 was found to have a reactivity similar to that of 4-(trimethylsilylmethyl)styrene (1 9). a) Present address: 4 3 l b , 3b: R = H: Is, 3s: R = Si(CH,), Experimental partAll procedures such as distillations, metalations, silylations and ring-opening reactions were carried out under purified nitrogen to eliminate oxygen and moisture.Materials-Commercial tetrahydrofuran 0. diisopropylamine @PA), 4-methylstyrene (MST), trimethylsilyl chloride (TMSC) and oxiranes were purified by conventional methods7). Commercial oxirane (5 a) was stirred over a mixture of potassium hydroxide and calcium hydride at -20 "C, then it was collected in atrap cooled with a liquid nitrogen bath. Purified 5 a was stored under nitrogen at -20°C. Commercial methyloxirane (Sb), ethyloxirane (Sc), 1.1-dimethyloxirane (5d) and tert-butyloxirane (5e) were purified by distillation over a mixture of potassium hydroxide and calcium hydride. 4-(Tkimethylsilyhnethyl)styrene (1 s) was prepared according to our previous paper'). Methods for purification of other materials were described in our previous paper '). Reaction between lithium diisopropylamide (LDA; 2) and oxiranes (5):One of the