Carbonyl compounds overview

Abstract The basic principles of the oxidative carbonylation reaction together with its synthetic applications are reviewed. In the first section, an overview of oxidative carbonylation is presented, and the general mechanisms followed by different substrates (alkenes, dienes, allenes, alkynes, ketones, ketenes, aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, phenols, amines) leading to a variety of carbonyl compounds are discussed. The second section is focused on processes catalyzed by Pdl2-based systems, and on their ability to promote different kind of oxidative carbonylations under mild conditions to afford important carbonyl derivatives with high selectivity and efficiency. In particular, the recent developments towards the one-step synthesis of new heterocyclic derivatives are described. 

Polyfluorooxiranes rearrange to carbonyl compounds in the presence of a wide range of catalysts. The nature of the product carbonyl compound depends on the structure of the epoxide and the catalyst an overview is given in Scheme 8. Monosubstituted perfluorooxiranes generally give acyl fluorides with Lewis bases, and trifluoromethyl ketones with Lewis acids. Symmetrically 2,3-disubstituted perfluorooxiranes give ketones with either Lewis acids or Lewis bases. In the presence of Lewis acids, unsymmetrically 2.3-disubstituted perfluorooxiranes give a 1 1 mixture of the two possible ketones. 

Rather than presenting a detailed review of the entire subject, an overview emphasizing experiments dealing with internal state selection and molecules of current interest will be given. The photochemistry and photophysics of formaldehyde will be discussed in much greater detail than will the other molecules presented in the final sections. The authors believe this to be justified on the basis of the large volume of state-selective work amassed recently on formaldehyde, and its unique character as the prototype carbonyl compound. The other molecules discussed are those which the authors believe to be of "current" interest. Of course, the fault of omission is inevitable in view of the practical limitation on space. 

Reductive alkylation is an effective method to synthesize secondary and tertiary amines from primary amines and hence is practiced commercially for the synthesis of a variety of fine and specialty chemicals. These inclnde corrosion inhibitors snch as the derivatives of cyclohexylamine, mbber chemicals such as A-(l,3-dimethylbutyl)-A -phenyl-p-phenylenediamine (6-PPD see Figure 15.13), pharmaceutical intermediates, dye intermediates, and pesticides [66-70]. The reaction starts ont as the condensation of an amine with a carbonyl compound followed by rednction of the intermediate imine (a Schiff base) to the desired amine. If the carbonyl componnd has an a-proton that can be abstracted, this secondary amine can be further reduced to tertiary amine [65]. Dne to the relatively small volume of such chemicals, the production is nsnally achieved in a batch process over a heterogeneous catalyst at pressures of 5 to 35 bar and temperatures of 323 to 423 K. Nishimura [71] provides an excellent overview of the literature for the synthesis of primary, secondary, and tertiary amines via reductive alkylation. 

In modern organic synthesis Dess-Martin periodinane (DMP, structure 800 in Scheme 3.316) has emerged as the reagent of choice for the oxidation of primary and secondary alcohols to the respective carbonyl compounds. DMP is commercially available or can be conveniently prepared by the reaction of IBX with acetic anhydride (Section 2.2.3.2) [1211]. The synthetic applications of DMP have been summarized in several overviews [1102,1104,1212,1213]. 

There is a wealth of literature information over the past centuiy in relation to mechanisms of acid-catalysed processes sueh as hydrolyses or solvolyses. In particular, the seminal work of Bell, Eigen and Jencks, clearly delineated all the mechanistic options for the reaction of carbonyl compounds with nucleophiles, and established the key criteria that influence specific and general acid-catalysed processes. In the following two sections, we overview only recent examples of homogeneous acid-catalysed reactions. 

In Chapter 8, which is complementary to the previous chapter, the direct arylation at the a-position of carbonyl compound substrates (e.g., amides and esters) is discussed. Once again, the catalytic systems and experimenttil conditions are carefully overviewed. 

Several reviews on allylboron compoimds and odier allylmetal reagents and their additions to carbonyl compoimds and imines have appeared [1-6], including two excellent chapters in a book from Wiley-VCH [1,2]. Accordingly, diis chapter does not aim to provide a comprehensive accoimt on die chemistry of allylboronates, but presents instead an overview of die main preparative methods for allylboronates, with particular focus on advances reported in die past five years, and on several recent synthetic applications such as the Lewis add-catalyzed additions to carbonyl compounds and tandem allylation reactions. 

Scheme 1.33 General overview of the gold(I)-catalyzed addition of carbonyl compounds to 1,6-enynes...

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