Bearings suitability

Carbonylation of alkenes bearing suitable functional groups proceeds regio-selectively. Carbonylation of vinylsilane and / -substituted vinylsilanes pro-... 

Direct or rigid couplings Flexible couplings Delayed-action couplings Construction and principle of operation Belt drives Checking the suitability of bearings Suitability of rotors for pulley drives... 

Transition metals have been used to trap and stabilize many different types of reactive intermediates, such as carbenes. Reactive silicon intermediates have only recently yielded to this approach. In the case of alkenes, for instance, transition metal complexes are generally made by exposing the alkene to a transition metal bearing suitable leaving groups (e.g., carbonyl). Unlike carbon-based intermediates, however, silicon-based analogs have been very difficult to prepare until recently. Unless... 

The most important method for the synthesis of 3i/-pyrazoles is by 1,3-dipoIar cycloaddition between a diazo compound and an alkyne, although alkenes bearing suitable leaving groups have also been used. Other methods include the cyclization of vinyldiazo compounds, and the oxidation of pyrazolines. 

B. From Diazo Compounds and Alkenes Bearing Suitable Leaving Groups... 

Reductive radical cyclization and tandem radical addition/cyclization reactions catalyzed by Ni(II) complexes, such as Ni(cyclam)(C104)2 98a, were studied starting in the 1990s by Ozaki s group [128]. The reaction conditions are applicable to alkyl and aryl halides bearing suitable positioned olefin units. Iodides and bromides can be used in some cases even aryl chlorides were successfully applied. The field was reviewed recently, and thus only more recent results are summarized here [19, 20]. 

Of special interest at present are phenolic compounds bearing suitable substituents which can undergo intramolecular cyclization induced by DIB. For example, whereas 4-hydroxybiphenyls normally gave in methanol the expected quinone ethers, when the aryl group had an o-alkenyl moiety, spiroannulated products resulted, with carbon-carbon bond formation [42] ... 

The reaction of oxazolines (331) derived from L-serine with diethylphosphite leads to a mixture of racemic a- and p-phosphono alanines (332) and (333). This new reaction proceeds without the use of any halogenated intermediate, and offers a simple route for various phosphonoamino acids bearing suitable protecting groups (Scheme 89). " ... 

Fig. 3 shows the routes by which components bearing suitable recognition sites lead to the formation of rotaxanes ... 

In substrates bearing suitable functionality that could lead to internal nucleophilic attack by an oxygen, even a carbonyl oxygen, excellent regioselectivity may occur. Equation 1.31 illustrates an example of a ketone playing such a role [27]. Such an effect can even lead to hydration at the more hindered alkyne as shown in... 

Typically, syntheses start from 1,2-difunctional benzenes bearing suitable groups. 

A macromolecule bearing suitable ligand groups or substituents can interact with a metal part (metal ion, metal complex) by covalent, coordinative, ionic or 7i-complex interactions as schematically shown in Fig. 5-1 [1-5], A great variety of macromolecules can be employed for the binding of the metal part (Section 1.2.1) ... 

C.i.a. Sequential Hydroarylation (Hydroalkenylation)/Cyclization. Since the cis stereochemistry of addition pushes the substituents of the acetylenic moiety to the same side of the olefinic double bond, a cyclization reaction can follow the addition step when these substituents bear suitable nucleophilic and electrophilic centers, and the whole process resembles a valuable straightforward methodology for the preparation of cyclic compounds (Scheme 20). Cyclization can occur under hydroarylation(hydroalkenylation) conditions—either before or after the substitution of the carbon-hydrogen bond for the carbon-palladium bond—or by subjecting the isolated hydroarylation(hydroalkenylation) product to suitable reaction conditions. This strategy has been employed successfully to develop new routes to various heterocycles. 

The Pd-catalyzed hydrovinylation reaction has received relatively much less attention, as it often favors the formation of linear products. However, recent work has proved that Pd complexes bearing suitable ligands could catalyze hydrovinylation reactions at room temperature, favoring the formation of branched products. However, considerable efforts are still required for developing highly efficient asymmetric versions of these reactions. 

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