Activation 1,2-insertion

As can be seen in the scheme below, insertion reactions of aldehydes to the C-H bond of aromatic ketimines by using a rhenium catalyst provided benzo[c]furans via a mechanism involving consecutive steps of C-H bond activation, insertion of aldehyde, intramolecular nucleophilic cyclization, reductive elimination, and elimination of aniline <06JA12376>. 

Depending on the nature of the substrates, selectivity could be completely reversed between the two isomeric products. For example, switching R1 group between Buc and Ph gave high yields of the first and second product structures, respectively. The authors noted that the reaction did not proceed if the imine contained an ortho-MeO group at R2 or if the imine was replaced with an aldehyde, oxime, or hydrazone. The catalytic cycle is initiated by C-H activation of the imine, that is, the formation of a five-membered metallocycle alkyne insertion affords the intermediate drawn in Scheme 69. It is noteworthy that this is the first report of catalytic synthesis of indene derivatives via a C-H insertion mechanism (C-H activation, insertion, intramolecular addition). 

According to isotope studies the rate-determining step of this sequence is the reductive elimination, and all other reactions (C-H activation, insertion of alkene) are reversible. The first indication of this behaviour was the H/D exchange of the ortho proton of acetophenone. Secondly, and perhaps useful for many other systems, was the kinetic isotope effect observed for 13C natural... 

The preparation of hollow microneedles affords the ability to combine the microneedle array with microfluidic channels to facilitate active insertion of the medicament into various layers of skin. This serves to increase the volume of medicament entering the skin, as opposed... 

Koshechko, V.G. and Kiprianova, L.A. (1999) Electrochemically activated insertion of fluo-roalkyl groups into organic and inorganic substrates. Theor. Exp. Chem. (Translation of Teoreticheskaya i EksperimentaTnaya Khimiya) 35,18-36. 

The composite cathode usually consists of an inert conducting material, the polymer/salt electrolyte, and the solid active insertion particles. The key requirements for a material to be successfully used as a cathode in a rechargeable lithium battery are as follows ... 

For alkynes, an electrophilic activation/insertion pathway leads to the Markovnikov product, whereas an alkyne/vinylidene isomerization pathway is specific towards anti-Markovnikov addition products [4—6]. Some insightful studies on elementary steps of the above mechanisms will now be presented. 

When replacing the terminal allenes with internal alkynes as the reaction components, the Rh-catalyzed C—H activation/insertion reaction of aromatic ketimines could also work well. Tran and Cramer described an asymmetric... 

Graph The Formal Graph represents two poles, each one with its three state variables, plus a new variable called activity, inserted into the capacitance path in a separate node. This variable is in charge of the interaction between the poles in being connected to the activity of the other pole. 

The selected reactivity insertion rate is as moderate as that achieved by actively inserted control rods in conventional fast reactors. The maximum thermal transient of the primary circuit in reactor start-up (10 K/min) is similar to that observed in a cold shock transient with scram of the conventional land-based reactors (typically 5 to 10 K/min). The role of the quick LEMs in this case is to restrict the power overshoot by 2 hours after the reactor start-up. 

Oxygen.— Photochemically induced insertion of molecular oxygen into the Co—C (T-bond of optically active 2-butylpyridine cobal oxime occurs with complete race-mization and the loss of optical activity can be attributed to a free-radical mechanism for which evidence has been obtained. Re-investigation of the corresponding reaction of O2 with 2-hydroxy-1-phenethylpyridine cobaloxime, which was originally reported to yield an optically active insertion product, also resulted in isolation of a racemic complex and the mechanistic details of these reactions at present remain obscure. 

Substituted benzaldehydes can be self-coupled oxidatively to give C(3)-substituted phthalides (146), using a rhodium(III)/aniline dual catalysis. The cascade ortho-C-M- (g) activation/insertion/annulation sequence can also be used in a heterocoupling sense with a second aldehyde. The dual catalysis allows plenty of scope for generating an enantios-elective version. 

When the reaction of Ai-sulfonyl aryl aldimines and alkynes was carried out in the presence of 5 mol% of [RuCl2(p-cymene)]2, 20 mol% of AgSbFg, 10 mol% TsNH2 and 4 equiv. of AcOH in dioxane at 95°C, after 20 h, no isoquinoline derivative was obtained as for ketimines (Scheme 20), but indenamine derivatives were obtained instead resulting from C-H bond activation, insertion of alkyne, and C-C bond formation [(Eq. 104)] [196]. 

Normally acid would be allowed to soak for some time and then back-produced if possible along with the impairing products. One of the advantages of using coiled tubing is that it can be inserted against well head pressure so the well does not have to be killed a potentially damaging activity. 

The full ab-initio molecular dynamics simulation revealed the insertion of ethylene into the Zr-C bond, leading to propyl formation. The dynamics simulations showed that this first step in ethylene polymerisation is extremely fast. Figure 2 shows the distance between the carbon atoms in ethylene and between an ethylene carbon and the methyl carbon, from which it follows that the insertion time is only about 170 fs. This observation suggests the absence of any significant barrier of activation at this stage of the polymerisation process, and for this catalyst. The absence or very small value of a barrier for insertion of ethylene into a bis-cyclopentadienyl titanocene or zirconocene has also been confirmed by static quantum simulations reported independently... 

The 7V-methylbenzo[( e]quinoline 426 was prepared by trapping the insertion product of an internal alkyne with a tertiary dimethylamine. One methyl group is eliminated. The dimethylaminonaphthalene-Pd complex 427 is an active catalyst and other Pd compounds are inactive[290a]. 

Acyi halides are reactive compounds and react with nucleophiles without a catalyst, but they are activated further by forming the acylpalladium intermediates, which undergo insertion and further transformations. The decarbonyla-tive reaction of acyl chlorides as pseudo-halides to form the aryipalladium is treated in Section 1,1.1.1. The reaction without decarbonylation is treated in this section. 

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