Aldehydes continued alkylation reactions

Photochemical reactions of the aldehydes and alkyl nitrites generate more radicals and continue the chain of reactions. 

As the text continues to develop the chemistry of aldehydes and ketones, you will now see how the carbon adjacent to a carbonyl group can become nucleophilic. First, reactions of these new nucleophiles with common electrophiles like luiloalkiines will be covered alkylation reactions. More important arc reactions of the nucleophilic a-carbons of one carbonyl compound with electrophilic carbonyl carbons of another. They are generically termed carbonyl condensation reactions. You see them here for aldehydes and ketones the aldol condensation. (In a later chapter you will be introduced to the analogous reaction of carboxylic esters the Claisen condensation.) The products of aldol condensations are a, j3-un.saturatcd aldehydes and ketones, which contain additional sites of electrophilic and potential nucleophilic character. 

Organotetracarbonylferrates, [RFe(CO)4], continue to find use in organic synthesis. A new synthesis of a-diketones consists of the reaction of aldehydes with alkyl halides and [Fe(CO)s]. The aldehyde, protected as the ethylenedithioacetal, is treated with butyl-lithium and [Fe(CO)s] to generate the acyltetracarbonylferrate (25) which then reacts with the alkyl halide to give the a-diketone in an overall yield of around 60%. [RFe(CO)4] reacts with Michael-type acceptors to give the expected product in about 90% yield [equation (10)]. ... 

In 2012, Xu and co-workers continued to report a Cu-catalyzed aerobic N-alkylation reaction of sulfonamides, anilines and heteroarylamines with alcohols under air (Eq. 61) [192]. The authors evaluated the effects of the additives on the reaction. They not only observed the promoting effect of air, but also found that aldehyde contamination in substrate alcohols could also lead to more efficient reactions either under either air or under nitrogen. Besides, they observed the successful oxidation of alcohol by Cu(ll) under anaerobic conditions (Eq. 62). 

The first synthesis 104, 105) of racemic thienamycin by the Merck group made use of the azetidinone (113) derived from acetoxybutadiene and chlorosulphonyl isocyanate (CSI). Reduction, hydrolysis and condensation with acetone gave the 1,3-tetrahydrooxazine (114). Introduction of the hydroxyethyl side chain by way of an aldol condensation produced predominantly the thermodynamically more stable tra s-P-lactam (115) as a mixture of R)- and (5)-isomers in the side chain. On removal of the acetone residue a proportion of the unwanted (5)-isomer crystallised from the mixture. The synthesis was continued with the mixture by way of the aldehyde (116) and the thio-acetal (117). Bromination, elimination and introduction of the iV(l) malonate residue gave (119) ready for an intramolecular alkylation reaction. 

Concurrent with acetic anhydride formation is the reduction of the metal-acyl species selectively to acetaldehyde. Unlike many other soluble metal catalysts (e.g. Co, Ru), no further reduction of the aldehyde to ethanol occurs. The mechanism of acetaldehyde formation in this process is likely identical to the conversion of alkyl halides to aldehydes with one additional carbon catalyzed by palladium (equation 14) (18). This reaction occurs with CO/H2 utilizing Pd(PPh )2Cl2 as a catalyst precursor. The suggested catalytic species is (PPh3)2 Pd(CO) (18). This reaction is likely occurring in the reductive carbonylation of methyl acetate, with methyl iodide (i.e. RX) being continuously generated. 

Chapters 26-29 continue the theme of synthesis that started with Chapter 24 and will end with Chapter 30. This group of four chapters introduces the main C-C bond-forming reactions of enols and enolates. We develop the chemistry of Chapter 21 with a discussion of enols and enolates attacking to alkylating agents (Chapter 26), aldehydes and ketones (Chapter 27), acylating agents (Chapter 28), and electrophilic alkenes (Chapter 29). 

Introduction of heteroatoms, e. g. N, S, or O, into hydrocarbon molecules adds substantial value, and new routes for such reactions are of continuous interest to the chemical industry. The two main classes of aromatic N-containing hydrocarbons are the arylamines and the aromatic N-heterocyclic compounds. The aryl-amines, which are required industrially, are manufactured by nitration of aromatics to nitroaromatics, followed by hydrogenation to arylamines [1,2]. Because of the lower demand for aromatic heterocycles than for arylamines, coal tar is still an important source of pyridine and methylpyridines (picolines). Increasing demand for aromatic heterocyclic compounds has led to processes in which aldehydes and ketones are condensed with NH3 to furnish pyridine and alkylated pyridines [3,4]. 

Here, R, represents an alkyl group containing one carbon atom less than R, so that R,0- = RiCH2CK The net reaction converts one molecule of n-alkane into one molecule of ketone and aldehyde each, and it oxidizes three molecules of NO to N02. The subsequent photodissociation of N02 is the source of ozone in photochemical smog. Note that the OH radical initiating the reaction sequence is regenerated so that it can continue the chain reaction. 

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