Part I. Studies in the Ring Closure of Selected Alkenyldichlorosilanes. Part II. Complete Reduction of Aromatic Esters to Methyl Groups by the Trichlorosilane – Tripropylamine Combination. Part III. Ketone Formation in Reversible Grignard and Organolithium Reactions.

EDWARD CASIMER MOZDZEN, Purdue University

Abstract

(1) The chloroplatinic acid-catalyzed intramolecular hydrosilyl- ations (ring closure) of the isomeric [2-(Cyclohexenyl)ethyl]dichloro- silanes were studied. The products, trans- and cis-7,7-dichloro-7- silabicyclo[4.3.0]nonane were separated and identified by comparison of the dimethyl derivatives to authentic samples. The isomer distribution was related to the position of the double bond in the starting material. The stereochemistry of the products was assigned by variable temperature NMR of the dimethyl derivative.Dichlorosilane was added to 1,4-cyclohexadiene giving 3-cyclo- hexenyldichlorosilane as the major product. This is the same product produced from the addition of dichlorosilane to 1,3-cyclohexadiene. Unlike the erratic yields obtained from the latter reaction, the addition to the 1,4- system afforded good yields and resulted in a good large scale synthesis of 3-cyclohexenyldichlorosilane.The ring-closed product, 7,7-dichloro-7-silanorbornane was derivatized to the 7,7-dimethyl, 7,7-diphenyl, and 7,7-dihydrido-7- silanorbornanes. The last of these was capable of undergoing hydro- silylation with terminal olefins, but in poor yields.(II) Trimethylsilyl benzoate was treated with trichlorosilane and tripropylamine giving benzyltrichlorosilane as the major product. Work by other investigators indicated that esters could be cleaved by iodotrimethylsilane or phenyltrimethylsilane-iodine, to form tri- methylsilyl esters. This reaction was combined with the above "reductive silylation" procedure and the products were hydrolyzed by base to afford a unique "one pot" reduction of aromatic esters to toluene derivatives. An investigation of the mechanisms of the above cleavage reactions contributed an important modification which increased the rate of cleavage dramatically.(III) The reversal of the lithium and magnesiumbromo alkoxides of dialkyl-a-methallylcarbinols often produced varied amounts of ketone. The ketone that formed always had lost the butenyl moiety. In general, the yields of ketone were the highest when the rate of reversal was slow and the ketone was enolizable. The fact that ketone was present in the reversal medium as its enolate was proved by trap- ping it as the trimethylsilylenol ether.

Degree

Ph.D.

Subject Area

Organic chemistry

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