Proton and carbon-13 nuclear magnetic resonance characteristics of substituted silacyclopentanes

Structures and mechanisms of formation of the major side products from the preparation of 4,4-dimethylcyclohex-2-enone by the potassium hydroxide promoted annelation of methyl vinyl ketone and isobutyraldehyde

“…However, for compounds 3-5 at least two reasonable mechanistic interpretations can be advanced for the generation of each substrate. 16 Similar results have been reported for [1,3] and [1,5] sigmatropic rearrangement^. In Scheme I, the enolate 6 is generated from enone 1 and subsequently alkylated by either isobutyraldehyde or methyl vinyl ketone to produce species 7 and 8, respectively.…”

“…In each case deuterium exchange to give 15a-18a was complete after 1 h, and no further changes resulted after 24 h. Chem. "Carbon-13 NMR Spectroscopy", Academic Press: New York, 1972; p 290. funnel charged with 1.42 g (0.02 mole) of isobutyraldehyde, 1.0 mL of HzO, and enough CH30H to bring the total volume to 5 mL were placed 0.16 g of potassium hydroxide, 1.0 mL of CH30H, and 2.42 g (0.02 mol) of 4,4-dimethylcyclohex-2-enone (1). 18: ref 7. (19) The carbon-13 NMR chemical shifts have been reported for compounds 1, 15, and 16 [Torri, J.;Azzaro, M. Bull.…”

“…0022-326317911944-4050$01.00/0 nelation reaction involving methyl vinyl ketone and isobutyraldehyde (eq 1) ,1-8 although the enamine approachg (1) Franke, W.; Bueren, J. German Patent 833645, 1952. The method usually chosen for the preparation of 1 has been the base-promoted an-'Dedicated to Professor William G. Dauben on the occasion of his 60th birthday.…”

“…In the latter proposal (Scheme IV), keto alkoxide 7 isomerizes to hydroxy enolate 13, which then undergoes a [1,5] sigmatropic shift of hydrogen to produce the hydroxy enolate 14, which upon protonation affords 4. The methoxy derivative 2 is probably produced by the conjugate addition of methoxide anion to enone 1 in a straightforward fashion.…”

Synthesis of Silyl Enol Ethers and Their Aldol Reaction Utilizing 2,5-Dimethyl-1-silacyclopentane and 2,5-Diphenyl-1-sila-3-cyclopentene Derivatives.

“…1 H-NMR analysis of the product. Isomer ratio of 1-chloro-2,5-diphenyl-1-sila-3-cyclopentene(2a) was 5.5 ( cisA/cisB).…”