Related reactions

Enantioselective Mannich reactions are widely utilized for the construction of 

Q acidic sites basic sites. hydrogen bonds 

The present catalytic reaction was applicable to ortho, meta, and para substituted 

N Boc protected arylimines and the corresponding products were obtained in 

The creation of a new structural motif of chiral phosphoric acids is a challenging 

There are several reactions which are known which are conceptually related to carbene reactions but which in general do not actually involve carbenes or even carbenoid intermediates. Usually these reactions are processes in which the potential generation of a carbene is circumvented by a concerted rearrangement process. An important example of this type of reaction is the thermal and photochemical reactions of acyl diazo compounds. Examples of carbene reactivity of a-diazoesters 

There are several experimental methods for effecting the Wolff rearrangement. The classical technique for preparation of acids or esters involves thermal decomposition in the presence of silver oxide in an aqueous solution (for acids) or an alcohol (for esters). At least for unsaturated diazoketones, the silver oxide seems to direct the reaction toward the rearrangement pathway in preference to carbenoid addition.Photolysis in nonnucleophilic solvents generates the ketene, which can undergo subsequent reactions in situ or, if sufficiently stable, be isolated. 

The photolysis of cyclic a-diazoketones results in ring contraction by a process which is analogous to the Wolff rearrangement. The ring contraction leads to a ketene intermediate, which is usually isolated as an ester. 

The chemistry of metal carbene and carbyne complexes has undergone very rapid development since the sixties and olefin metathesis reactions now form part of a much larger family of [2 + 2] metathesis reactions between multiply bonded compounds. In Section 4.2 we shall briefly consider this wider context. Some examples will be given of the use of stoichiometric metathesis reactions of such complexes in organic synthesis (Dotz 1984 Schubert 1989). 

Finally we consider how three-membered ring compounds may be involved in both initiation and termination reactions in olefin metathesis Section 4.4. 

2 [2 + 2] reactions between compounds containing multiple bonds 

Such reactions between compounds containing double bonds may be represented in shorthand form by eqn. (1). 

The reactants may also contain triple bonds in place of one or both double bonds. 

CHAPTER 10 REACTIONS INVOLVING CARBOCATTONS, CARBENES, AND RADICALS AS REACTIVE INTERMEDIATES 

The diphenyl analog shows about 20-30% rearrangement.153 a-D i azocyc I o hex an one gives no evidence of an oxirene intermediate, since all the label remains at the carbonyl carbon.154 

The main synthetic application of the Wolff rearrangement is for the one-carbon homologation of carboxylic acids.155 In this procedure, a diazomethyl ketone is synthesized from an acyl chloride. The rearrangement is then carried out in a nucleophilic solvent which traps the ketene to form a carboxylic acid (in water) or an ester (in alcohols). Silver oxide is often used as a catalyst, because it seems to promote the rearrangement over carbene formation.156 157 158 

Such an expression is expected to be valid when the promoting action is limited to the perimeter of the promoter patches on the metal surface. Three steps can in principle be influenced by promoters (transition metal oxides)  

The production of C2 alcohols is higher on the metals left from the diagonal in Group VIII (Fe, Co, Ru) since these metals tend to accumulate CHX groups on the whole metallic surface. Rhodium is most suitable for producing ethanol its CO dissociation activity is weak and thus the CHX units are preferentially formed on the metal surface round the patches of the promoting oxide. 

It is perhaps worthwhile noting that the promoter patches on the metal can be either created during the wet steps of the catalyst preparation, or when a transition metal oxide is used as a support, they can be created by migration of the support material on the metal upon high temperature reduction. The metal surface can be kept almost completely covered in vacuo (SMSI effect) [52], but in the presence of CO or of the reaction mixture, the layer of oxide recrystallizes and the metal surface becomes accessible again from the gas phase [33]. 

This is an important industrial reaction, alone or in combination with others. The CH3OH production is often coupled to oxidation to formaldehyde, methanol to gasoline (Mobil) process, methanol to olefins process, carbonylation, etc. Due to this, a large volume of information already exists on catalyst preparation, kinetics, reactors and all other aspects of the related chemical technology [53]. However, let us concentrate our attention here on just one selected problem the role of the promoter and the nature of the active site on the metal on oxides catalysts. Let us mention in passing that pure metals (promoter free) most likely do not catalyze the synthesis. 

Ideas suggested in the literature concerning active sites can be subdivided into three main streams  

On gold film at 195 K a fast exchange was observed between CH3SiH3 and CH3SiD3, but no deuterium entered the methyl group.52 

Instead of 2,4-dialkopyrimidines, some other alkoxy heterocyclics capable of lactam-lactim tautomerism were used, e.g., 2-ethoxy-pyridine42,43 (36), 4-ethoxypyridine44 (37), and 3,6-dibenzyloxy-pyridazine45 (38). Treatment of a-acetobromoglucose with 36 gave 

The synthesis of maleic acid hydrazide riboside (42) has been accomplished45 by the Hilbert-Johnson reaction of 38 with 2,3,5-tri-O-benzoyl-D-ribofuranosyl chloride in toluene at 100° in the presence 

Pliml and F. Sorm, Collection Czech. Chem. Commun. 30, 3744 (1965). 

A high yield of 3-/3-D-ribofuranosyluric acid (45) has been obtained48,47 on treatment of tetrakis(triethylsilyl)uric acid (44) with benzobromoribofuranose at 50° in the presence of silver perchlorate in toluene as solvent, subsequent hydrolysis with methanol, and removal of the protecting benzoyl groups with methanolic ammonia. 

Similarly, treatment of 2-trimethylsilyloxypyridine (46) with a-acetobromoglucose and silver perchlorate in nitromethane at 20° yielded l-(2,3,4,6-tetra-0-acetyl-D-glucopyranosyl)-2-pyridone (47) as the sole product.46 47 On the other hand, 2-ethoxypyridine (vide supra) gave a mixture of 0- and V-glycosyl derivatives.42,43 

The extent to which the oxirene is formed depends on the structure of the diazo compound. For diazoacetaldehyde, photolysis leads to only 8% migration of label, which would correspond to formation of 16% of the product through the oxirene.  

Homogeneous Catalysis Mechanisms and Industrial Applications, Second Edition. Sumit Bhaduri and Doble Mukesh. 

In this chapter, we discuss the basic mechanisms and other details of a few industrial carbonylation processes. Among them, in terms of scales of production, acetic acid by methanol carbonylation and acetic anhydride by methyl acetate carbonylation are the two most important (reactions 4.1.1 and 4.1.2). 

The carbonylation of propyne (methyl acetylene) in methanol to give methyl methacrylate (MMA) was commercialized by Shell. There is also a carbonylation process for the manufacture of phenyl acetic acid from benzyl chloride. A novel carbonylation process, which reduces the E factor significantly, has been reported for the drug ibuprofen. 

Apart from these, there are two other catalytic reactions that involve CO as one of the reactants. These are the water gas shift (WGS see Section 1.6.4) and the Fischer-Tropsch (FT) reactions. Industrially homogeneous catalysts are not used for these reactions. However, for explaining the formation of by-products in homogeneous catalyst-based industrial processes, they are relevant. 

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A number of related reactions of hydrocarbons are catalyzed by acidic oxide types of materials. These include the cracking of high molecular weight... 

The classic example is the butadiene system, which can rearrange photochemi-cally to either cyclobutene or bicyclobutane. The spin pairing diagrams are shown in Figure 13. The stereochemical properties of this reaction were discussed in Section III (see Fig. 8). A related reaction is the addition of two ethylene derivatives to form cyclobutanes. In this system, there are also three possible spin pairing options. 

THE cvcLOBUTADENE-TETRAHEDRANE SYSTEM. A related reaction is the photoisomerization of cyclobutadiene (CBD). It was found that unsubstituted CBD does not react in an argon matrix upon irradiation, while the tri-butyl substituted derivative forms the corresponding tetrahedrane [86,87]. These results may be understood on the basis of a conical intersection enclosed by the loop shown in Figure 37. The analogy with the butadiene loop (Fig. 13) is obvious. The two CBDs and the biradical shown in the figure are the three anchors in this system. With small substituents, the two lobes containing the lone electrons can be far... 

In contrast to IR and NMR spectroscopy, the principle of mass spectrometry (MS) is based on decomposition and reactions of organic molecules on theii way from the ion source to the detector. Consequently, structure-MS correlation is basically a matter of relating reactions to the signals in a mass spectrum. The chemical structure information contained in mass spectra is difficult to extract because of the complicated relationships between MS data and chemical structures. The aim of spectra evaluation can be either the identification of a compound or the interpretation of spectral data in order to elucidate the chemical structure [78-80],... 

In the development of the CAMEO system (Computer-Assisted Mechanistic Evaluation of Organic reactions) [8 it was decided to treat large classes of mechanistically related reaction types by separate modules. 

The next example shows how different search queries can be combined to shed more light onto a series of related reactions. A reaction substructure search for reactions that break a P-O bond provided 304 reactions as hits. Figure 10.3-27 shows one of the reactions in this hit list. 

Shapiro and Related Reactions Organic Reactions 1990, 39, 1 1976, 23, 405 - Reaction of a tosylhydrazone with a strong base to give an olefin. 

Friedel-Crafts and Related Reactions, Vols. I-IV (ed), 1963-1964. Carbonium Ions (ed. with Schleyer), Vols. I-V, 1968-1972. Friedel-Crafts Chemistry, 1973. 

The selectivity relationship merely expresses the proportionality between intermolecular and intramolecular selectivities in electrophilic substitution, and it is not surprising that these quantities should be related. There are examples of related reactions in which connections between selectivity and reactivity have been demonstrated. For example, the ratio of the rates of reaction with the azide anion and water of the triphenylmethyl, diphenylmethyl and tert-butyl carbonium ions were 2-8x10 , 2-4x10 and 3-9 respectively the selectivities of the ions decrease as the reactivities increase. The existence, under very restricted and closely related conditions, of a relationship between reactivity and selectivity in the reactions mentioned above, does not permit the assumption that a similar relationship holds over the wide range of different electrophilic aromatic substitutions. In these substitution reactions a difficulty arises in defining the concept of reactivity it is not sufficient to assume that the reactivity of an electrophile is related... 

Gilbert, E. E. 1965, Sulphonat ion and Related Reactions, Wiley New York... 

Allylic Rearrangement, Claisen Rearrangement, and Related Reactions Catalyzed by Pd(0) and Pd(II)... 

The rearrangements of various allylic compounds catalyzed by both Pd(II) and Pd(0) are treated in this section[491]. Related reactions such as the Carroll rearrangement are treated in Section 2.10.1 and the Pd(II)-catalyzed Cope rearrangement is treated in Chapter 5, Section 3. 

Dimerization and Telomerization of Conjugated Dienes and Related Reactions... 

Butyrolactones are prepared by intramolecular reaction of haloallylic 2-alkynoates. The a-chloromethylenebutyrolactone 301 is prepared by the intramolecular reaction of300[150,151]. 4 -Hydroxy-2 -alkenyl 2-alkynoates can be used instead of haloallylic 2-alkynoates, and in this reaction, Pd(II) is regenerated by elimination of the hydroxy group[152]. As a related reaction, the q-(chloromethylene)-7-butyrolactone 304 is obtained from the cinnamyl 2-alkynoate 302 in the presence of LiCl and CuCbflSS]. Isohinokinin (305) has been synthesized by this reaction[l 54]. The reaction is explained by chloro-palladation of the triple bond, followed by intramolecular alkene insertion to generate the alkylpalladium chloride 303. Then PdCb is regenerated by attack of CuCb on the alkylpalladium bond as a key step in the catalytic reaction. 

An Organic Syntheses preparation of 4-nitroindole may involve a related reaction. The condensation occurs in the presence of diethyl oxalate which may function by condensation at the methyl group. If this is the case, it must subsequently be lost by deacylation[17]. 

The next section explores the mechanism of nucleophilic addition to aldehydes and ketones There we 11 discuss their hydration a reaction m which water adds to the C=0 group After we use this reaction to develop some general principles we 11 then survey a number of related reactions of synthetic mechanistic or biological interest... 

Lithium diisopropylamide is commercially available Alternatively it may be prepared by the reaction of butyllithium with [(CH3)2CH]2NH (see Problem 14 4a for a related reaction)... 

Aldol Addition and Related Reactions. Procedures that involve the formation and subsequent reaction of anions derived from active methylene compounds constitute a very important and synthetically useful class of organic reactions. Perhaps the most common are those reactions in which the anion, usually called an enolate, is formed by removal of a proton from the carbon atom alpha to the carbonyl group. Addition of this enolate to another carbonyl of an aldehyde or ketone, followed by protonation, constitutes aldol addition, for example... 

Substitution of alkaline cyanates by isocyanates allows the preparation of 3-substituted hydantoias, both from amino acids (64) and amino nitriles (65). The related reaction between a-amino acids and phenyl isothiocyanate to yield 5-substituted 3-phenyl-2-thiohydantoiQS has been used for the analytical characterization of amino acids, and is the basis of the Edman method for the sequential degradation of peptides with concomitant identification of the /V-terminal amino acid. 

A related reaction sequence, which proceeds through a Curtius rearrangement, allows the transformation of a-cyano acids into hydantoins (66) ... 

Single-Carbon Insertion Reactions. Carbonylation, cyanidation, and "DCME," and related reactions are convenient general processes developed to bring about the transfer of organic groups from boron to a siagle-carbon atom. 

Methacryhc acid and its ester derivatives are Ctfjy -unsaturated carbonyl compounds and exhibit the reactivity typical of this class of compounds, ie, Michael and Michael-type conjugate addition reactions and a variety of cycloaddition and related reactions. Although less reactive than the corresponding acrylates as the result of the electron-donating effect and the steric hindrance of the a-methyl group, methacrylates readily undergo a wide variety of reactions and are valuable intermediates in many synthetic procedures. 

Acylation. A/-Acylation and related reactions ate brought about in straightforward ways with acyl chloride or acid anhydride, although the proximity of the carboxyl group may produce other reactions, eg, oxa2olinone formation, under some conditions. 

G. A. Olah, ed., Friedel-Crafts and Related Reactions, Wiley-Interscience, New York, 1964. 

Solvent for Displacement Reactions. As the most polar of the common aprotic solvents, DMSO is a favored solvent for displacement reactions because of its high dielectric constant and because anions are less solvated in it (87). Rates for these reactions are sometimes a thousand times faster in DMSO than in alcohols. Suitable nucleophiles include acetyUde ion, alkoxide ion, hydroxide ion, azide ion, carbanions, carboxylate ions, cyanide ion, hahde ions, mercaptide ions, phenoxide ions, nitrite ions, and thiocyanate ions (31). Rates of displacement by amides or amines are also greater in DMSO than in alcohol or aqueous solutions. Dimethyl sulfoxide is used as the reaction solvent in the manufacture of high performance, polyaryl ether polymers by reaction of bis(4,4 -chlorophenyl) sulfone with the disodium salts of dihydroxyphenols, eg, bisphenol A or 4,4 -sulfonylbisphenol (88). These and related reactions are made more economical by efficient recycling of DMSO (89). Nucleophilic displacement of activated aromatic nitro groups with aryloxy anion in DMSO is a versatile and useful reaction for the synthesis of aromatic ethers and polyethers (90). 

E. E. Gilbert, Sufonation and Related Reaction, Wiley-Interscience, New York, 1965, Chapt. 6. 

Fig. 18. Schematic representation of the catalytic cycle for ammoxidation of propylene and related reactions. and M2 represent the two metals in a...

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