Carbonyl compounds reactions between

With saturated carbonyl compounds, and especially with aromatic carbonyl compounds, reaction between the photoexcited carbonyl chromophore and alkenes results in the formation of four-membered cyclic ethers (oxetane). The addition of carbonyl compounds to alkenes to give oxetanes is often referred to as the Patemo-... 

Air oxidation of a variety of aliphatic and alkyl aromatic compounda air oxidation of p-nitrotoluene sulfuric acid substitution chlorination of a variety of organic compounds reaction between isobutylene and acetic acid oxidation of ethylene to acetaldehyde (Wacker processes) hydrochlorination of olehns absorption of phosphine in an aqueous soluhon of formaldehyde and hydrochloric acid acehc acid from the carbonylation of methanol oxidation of tri-alkyl phosphine dimerization of olefins. 

The Maillard Reaction. The Maillard reaction is probably one of the best known deteriorative reactions in the drying and storage of foods containing carbohydrates. The initial reaction is a carbonyl-amine reaction between the carbonyl group of the carbonyl compound (usually... 

Association between RMgX and Carbonyl Compounds Reactions of Benzophenone(s) with Grignard Reagents... 

The Schiff base or enamine reaction has been employed to modify aldehydes and ketones by condensation with a primary amine (reaction 1) and to condense primary amines with a carbonyl compound (reaction 2). A similar reaction between primary amines and carbon disulfide yields isothiocyanates or mustard oils (reaction 3). These three possibilities for derivative formation will be discussed in this chapter. 

The reaction between sodium acetylide in liquid ammonia solution and carbonyl compounds gives a-acetylenyl carbinols (compare Section 111,148), for example ... 

Intramolecular reactions between donor and acceptor centres in fused ring systems provide a general route to bridged polycyclic systems. The cts-decalone mesylate given below contains two d -centres adjacent to the carbonyl function and one a -centre. Treatment of this compound with base leads to reversible enolate formation, and the C-3 carbanion substitutes the mesylate on C-7 (J. Gauthier, 1967 A. Belanger, 1968). 

Pyrazolines can be prepared from the reaction between a hydrazine and two carbonyl compounds, one of them having at least one hydrogen atom a to the carbonyl group. Formally, these reactions correspond to the [NN + C + CC] class. However, if one considers the different steps in the ring formation, they more properly belong to the [CNN + CC] (Section 4.04.3.1.2(ii)), the [CCNN + C] (Section 4.04.3.1.2(i)), or the formation of one bond (Section 4.04.3.1.1) classes. 

Chapters 1 and 2. Most C—H bonds are very weakly acidic and have no tendency to ionize spontaneously to form carbanions. Reactions that involve carbanion intermediates are therefore usually carried out in the presence of a base which can generate the reactive carbanion intermediate. Base-catalyzed condensation reactions of carbonyl compounds provide many examples of this type of reaction. The reaction between acetophenone and benzaldehyde, which was considered in Section 4.2, for example, requires a basic catalyst to proceed, and the kinetics of the reaction show that the rate is proportional to the catalyst concentration. This is because the neutral acetophenone molecule is not nucleophihc and does not react with benzaldehyde. The much more nucleophilic enolate (carbanion) formed by deprotonation is the reactive nucleophile. 

There have been numerous studies of the rates of deprotonation of carbonyl compounds. These data are of interest not only because they define the relationship between thermodynamic and kinetic acidity for these compounds, but also because they are necessary for understanding mechanisms of reactions in which enolates are involved as intermediates. Rates of enolate formation can be measured conveniently by following isotopic exchange using either deuterium or tritium ... 

Secondary amines cannot form imines, and dehydration proceeds to give carbon-carbon double bonds bearing amino substituents (enamines). Enamines were mentioned in Chapter 7 as examples of nucleophilic carbon species, and their synthetic utility is discussed in Chapter 1 of Part B. The equilibrium for the reaction between secondary amines and carbonyl compounds ordinarily lies far to the left in aqueous solution, but the reaction can be driven forward by dehydration methods. 

Certain reactions between carbonyl compounds and nucleophiles are catalyzed by amines. Some of these reactions are of importance for forming carbon-carbon bonds, and these are discussed in Chapter 2 of Part B. The mechanistic principle can be illustrated by considering the catalysis of the reaction between aldehydes and hydroxylamine by aniline derivatives. 

The photochemistry of carbonyl compounds has been extensively studied, both in solution and in the gas phase. It is not surprising that there are major differences between the photochemical reactions in the two phases. In the gas phase, the energy transferred by excitation cannot be lost rapidly by collision, whereas in the liquid phase the excess energy is rapidly transferred to the solvent or to other components of the solution. Solution photochemistry will be emphasized here, since both mechanistic study and preparative applications of organic reactions usually involve solution processes. 

Schmidt reaction is the reaction between carbonyl compounds and hydrazoic acid in the presence of e.g. concentrated sulphuric acid... 

The mechanism of the reaction between a hydrocarbon organohthium compound and a carbonyl compound is well-documented [69] and has been suggested earlier for fluonne-contaming compounds [32, 68, 70] More recent studies on the mechanism have resulted in a better understanding of this reaction [71] (equauon 37)... 

The fluoride anion has a pronounced catalytic effect on the aldol reaction between enol silyl ethers and carbonyl compounds [13] This reacbon proceeds at low temperature under the influence of catalytic amounts (5-10 mol %) of tetra-butylammonium fluoride, giving the aldol silyl ethers in high yields (equation 11). 

Instead of the definition in Eq. (7-82), the selectivity is often written as log k,). Another way to consider a selectivity-reactivity relationship is to compare the relative effects of a series of substituents on a pair of reactions. This is what is done when Hammett plots are made for a pair of reactions and their p values are compared. The slope of an LEER is a function of the sensitivity of the process being correlated to structural or solvent changes. Thus, in a family of closely related LFERs, the one with the steepest slope is the most selective, and the one with the smallest slope is the least selective.Moreover, the intercept (or some arbitrarily selected abscissa value, usually log fco for fhe reference substituent) should be a measure of reactivity in each reaction series. Thus, a correlation should exist between the slopes (selectivity) and intercepts (reactivity) of a family of related LFERs. It has been suggested that the slopes and intercepts should be linearly related, but the conditions required for linearity are seldom met, and it is instead common to find only a rough correlation, indicative of normal selectivity-reactivity behavior. The Br nsted slopes, p, for the halogenation of a series of carbonyl compounds catalyzed by carboxylate ions show a smooth but nonlinear correlation with log... 

The Knorr pyrrole synthesis involves the reaction between an a-amino ketone 1 and a second carbonyl compound 2, having a reactive a-methylene group, to give a pyrrole 3. The amine 1 is often generated in situ by reduction of an oximino group. 

The Pictet-Spengler reaction is an acid-catalyzed intramolecular cyclization of an intermediate imine of 2-arylethylamine, formed by condensation with a carbonyl compound, to give 1,2,3,4-tetrahydroisoquinoline derivatives. This condensation reaction has been studied under acid-catalyzed and superacid-catalyzed conditions, and a linear correlation had been found between the rate of the reaction and the acidity of the reaction medium. Substrates with electron-donating substituents on the aromatic ring cyclize faster than the corresponding unsubstituted compounds, supporting the idea that the cyclization process is involved in the rate-determining step of the reaction. 

Chiral boron(III) Lewis acid catalysts have also been used for enantioselective cycloaddition reactions of carbonyl compounds [17]. The chiral acyloxylborane catalysts 9a-9d, which are also efficient catalysts for asymmetric Diels-Alder reactions [17, 18], can also catalyze highly enantioselective cycloaddition reactions of aldehydes with activated dienes. The arylboron catalysts 9b-9c which are air- and moisture-stable have been shown by Yamamoto et al. to induce excellent chiral induction in the cycloaddition reaction between, e.g., benzaldehyde and Danishefsky s dienes such as 2b with up to 95% yield and 97% ee of the cycloaddition product CIS-3b (Scheme 4.9) [17]. 

A simple approach for the formation of 2-substituted 3,4-dihydro-2H-pyrans, which are useful precursors for natural products such as optically active carbohydrates, is the catalytic enantioselective cycloaddition reaction of a,/ -unsaturated carbonyl compounds with electron-rich alkenes. This is an inverse electron-demand cycloaddition reaction which is controlled by a dominant interaction between the LUMO of the 1-oxa-1,3-butadiene and the HOMO of the alkene (Scheme 4.2, right). This is usually a concerted non-synchronous reaction with retention of the configuration of the die-nophile and results in normally high regioselectivity, which in the presence of Lewis acids is improved and, furthermore, also increases the reaction rate. 

Carbonyl compounds can undergo various photochemical reactions among the most important are two types of reactions that are named after Norrish. The term Norrish type I fragmentation refers to a photochemical reaction of a carbonyl compound 1 where a bond between carbonyl group and an a-carbon is cleaved homolytically. The resulting radical species 2 and 3 can further react by decarbonylation, disproportionation or recombination, to yield a variety of products. 

The nitro-dldolredcdon between nitrodlkdnes and carbonyl compounds to yieldfi-nitro alcohols was discovered in 1895 by Henry. Since dien, diis reaction has been used extensively in many important syndieses. In view of its significance, diere are several reviews on die Henry reaction." These reviews cover syndiesis of fi-nitro alcohols and dieir applications in organic synthesis. The most comprehensive review is Ref 3, which summarizes the literature before 1970. More recent reviews are Refs. 4 and 5, which summarize literatures on the Henry reaction published until 1990. 

The Sn2 alkylation reaction between an enolate ion and an alkyl halide is a powerful method for making C-C bonds, thereby building up larger molecules from smaller precursors. We ll study the alkylation of many kinds of carbonyl compounds in Chapter 22. 

Note the key difference between the base-catalyzed and acid-catalyzed reactions. The base-catalyzed reaction takes place rapidly because water is converted into hydroxide ion, a much better nucleophile. The acid-catalvzed reaction takes place rapidly because the carbonyl compound is converted by protonation into a much better electrophile. 

Each of the following substances can be prepared by a nucleophilic addition reaction between an aldehyde or ketone and a nucleophile. Identify the reactants from which each was prepared. If the substance is an acetal, identify the carbonyl compound and the alcohol if it is an imine, identify the carbonyl compound and the amine and so forth. 

Strategy The overall result of an enamine reaction is the Michael addition of a ketone as donor to an cr,/3-unsaturated carbonyl compound as acceptor, yielding a 1,5-dicarbonyl product. The C—C bond made in the Michael addition step is the one between the a- carbon of the ketone donor and the /3 carbon of the unsaturated acceptor. 

---