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NBS will react with alkenes 1 in aqueous solvents to give bromohydrins 2. The preferred conditions are the portionwise addition of NBS to a solution of the alkene in 50% aqueous DMSO, DME, THF, or tert-butanol at 0 °C. [3] Formation of a bromonium ion and immediate attack by water gives strong Markovnikov addition and anti stereochemical ...
In the Goldfinger mechanism, the purpose of the NBS is simply to maintain a very low concentration of molecular bromine, while in the Bloomfield mechanism, its purpose is the generation of the initial radical used in the reaction, [11] which again can be quite a difficult process. [12]
The mechanism of the Bartoli indole synthesis. The mechanism begins by the addition of the Grignard reagent (2) onto the nitroarene (1) to form intermediate 3. Intermediate 3 spontaneously decomposes to form a nitrosoarene (4) and a magnesium salt (5). (Upon reaction workup, the magnesium salt will liberate a carbonyl compound (6).)
Weinreb and Nahm originally proposed the following reaction mechanism to explain the selectivity shown in reactions of the Weinreb–Nahm amide. Their suggestion was that the tetrahedral intermediate (A below) formed as a result of nucleophilic addition by the organometallic reagent is stabilized by chelation from the methoxy group as shown. [1]
The four main categories are (1) nucleophilic attack on an alkene alkyne, or allyl ligand and (2) insertion of the alkene into the metal-amide bond. [11] Generic catalytic cycles appear below. Mechanisms are supported by rate studies, isotopic labeling, and trapping of the proposed intermediates. Common catalytic cycles for hydroamination
The aza-Cope rearrangements are predicted by the Woodward-Hoffman rules to proceed suprafacially. However, while never explicitly studied, Overman and coworkers have hypothesized that, as with the base-catalyzed oxy-Cope rearrangement, the charged atom distorts the sigmatropic rearrangement from a purely concerted reaction mechanism (as expected in the Cope rearrangement), to one with partial ...
Anxious airline flyers may well remember 2024 as the year their worst fears about the safety of air travel felt confirmed, as a series of unprecedented, and in some cases fatal, airplane incidents ...
In any of the pairwise mechanisms with olefin pairing as rate-determining step this compound, a secondary reaction product of C12 with C6, would form well after formation of the two primary reaction products C12 and C16. In 1974 Casey was the first to implement carbenes into the metathesis reaction mechanism: [27]