Vinyl hydrogen more reactive than benzyl hydrogen toward base in significantly twisted styrenes

Highly Activated Vinyl Hydrogen in a Significantly Twisted Styrene

“…2-Methyl-4-(2,6-dimethylphenyl)-4-triethylsilyl-3-buten-2-ol (11). To a solution of n-butyllithium (1.6 M solution in hexane, 1.0 mL, 1.6 mmol) was added tetramethylethylenediamine (TME-DA) (0.12 mL, 0.80 mmol) at 0 °C.…”

“…In a preliminary communication, as a new entry for the unique character of the twisted 1,3-dienes or styrene derivatives, we have reported that the novel example of the vinyl hydrogens in the significantly twisted styrenes are more reactive than the benzyl hydrogens toward a base. 11 In this paper, we describe the full details of the base treatment of various kinds of twisted styrenes, along with a discussion on the correlation between the magnitude of the twist and the reactivity of the vinyl hydrogens. The mechanistic consideration of the proton abstraction and the formation of the products, whose vinylic positions were substituted by deuterium or the triethylsilyl group, is also described.…”

“…In a preliminary communication, as a new entry for the unique character of the twisted 1,3-dienes or styrene derivatives, we have reported that the novel example of the vinyl hydrogens in the significantly twisted styrenes are more reactive than the benzyl hydrogens toward a base …”

Mixed AggregAte (MAA): A Single Concept for All Dipolar Organometallic Aggregates. 2. Syntheses and Reactivities of Homo/HeteroMAAs

“…It is known that LIC-KOR and, sometimes more efficiently, LIC-NaOR (1:1 BuLi· t -BuONa) are able to metalate vinylic C–H bonds. The presence of heteroatoms such as in cyclic vinyl ethers, 4 H -pyrans, and 1,4-dihydropyridines favors the reaction (Table ). ,,, Starting from twisted styrenes, it has been noted by Katsumura and co-workers that vinyl hydrogens can be more easily abstracted by LIC-KOR than benzyl hydrogens . Metalations of 1-heteroalkyl-1,3-butadienes using LIC-KOR followed by interception with isothiocyanates, either followed by S -alkylation or by hydrolysis to afford 2-imino-5,6-dihydro-2 H -thiopyrans, were reported (Scheme ).…”

“…717,730ab,730ad,747 Starting from twisted styrenes, it has been noted by Katsumura and co-workers that vinyl hydrogens can be more easily abstracted by LIC-KOR than benzyl hydrogens. 748 Metalations of 1-heteroalkyl-1,3-butadienes using LIC-KOR followed by interception with isothiocyanates, either followed by S-alkylation 749 or by hydrolysis to afford 2-imino-5,6-dihydro-2H-thiopyrans, 750 were reported (Scheme 178).…”