Condensation with secondary

Thioindoxyl condenses with various primary aliphatic and primary and secondary aromatic amines to give 3-aminobenzo[6]thio-phenes 539,541, 553,554 condensation with secondary aliphatic amines... 

Condensation with Secondary Hydroxyl Groups of Sugars.124... 

If a molecule contains both aldehydic and ketonic functions, reaction with a secondary amine occurs at the former115-117. Acyloins (a-hydroxyketones) condense with secondary amines to give a-aminoketones rather than enamines118. 

An interesting reaction is the o-aminophenol rearrangement of acylfuran-enamines described by Birkofer and Daum.340 2-Acylfurans condense with secondary amines in the presence of a small quantity... 

Even if the a hydrogen of an amine is not highly acidic, its activation is possible by condensation with a special type of carbonyl compound. Grigg s idea (86CC602) is given in Eq. (12), in which carbonyl compounds bearing a conjugated C=X moiety (X = heteroatom) are condensed with secondary... 

Enamination. Ketone condensation with secondary amines using BSA [or bis(trimethylsilyl)urea] as dehydrating agent is quite advantageous. lodomethane is also present. 

The above mentioned methods for preparation of cyclic bis-amides were patterned after peptide chemistry reactions where amide bonds dominate. Also in peptide chemistry, DCC, and DCC plus 1-hydroxybenzotriazole (HOBT) have been used in amide formation reactions. Using this procedure, 16-membered peraza-crowns have been prepared in 50-55% yields for the cyclization step (Vellacio et al., 1977). The carboxyl group can also condense with secondary amines in DMF in the presence of 1.1 mol of DCC and 1.2 mol of HOBT per mole of the dicarboxylic acid (Krakowiak et al., 1989). 

Condensations with secondary amines give enamines... 

The most important reaction of the diazonium salts is the condensation with phenols or aromatic amines to form the intensely coloured azo compounds. The phenol or amine is called the secondary component, and the process of coupling with a diazonium salt is the basis of manufacture of all the azo dyestuffs. The entering azo group goes into the p-position of the benzene ring if this is free, otherwise it takes up the o-position, e.g. diazotized aniline coupled with phenol gives benzeneazophenol. When only half a molecular proportion of nitrous acid is used in the diazotization of an aromatic amine a diazo-amino compound is formed. 

Formyl derivatives. Formic acid condenses with primary and secondary amines to yield formyl derivatives ... 

The condensation of aldehydes or ketones with secondary amines leads to "encunines via N-hemiacetals and immonium hydroxides, when the water is removed. In these conjugated systems electron density and nudeophilicity are largely transferred from the nitrogen to the a-carbon atom, and thus enamines are useful electroneutral d -reagents (G.A. Cook, 1969 S.F. Dyke, 1973). A bulky heterocyclic substituent supports regio- and stereoselective reactions. 

There also exists an acidregioselective condensation of the aldol type, namely the Mannich reaction (B. Reichert, 1959 H. Hellmann, 1960 see also p. 291f.). The condensation of secondary amines with aldehydes yields Immonium salts, which react with ketones to give 3-amino ketones (=Mannich bases). Ketones with two enolizable CHj-groupings may form 1,5-diamino-3-pentanones, but monosubstitution products can always be obtained in high yield. Unsymmetrical ketones react preferentially at the most highly substituted carbon atom. Sterical hindrance can reverse this regioselectivity. Thermal elimination of amines leads to the a,)3-unsaturated ketone. Another efficient pathway to vinyl ketones starts with the addition of terminal alkynes to immonium salts. On mercury(ll) catalyzed hydration the product is converted to the Mannich base (H. Smith, 1964). 

Pyrrohdinone can also condense with primary or secondary amines. 

Sulfation by sulfamic acid has been used ia the preparation of detergents from dodecyl, oleyl, and other higher alcohols. It is also used ia sulfating phenols and phenol—ethylene oxide condensation products. Secondary alcohols react ia the presence of an amide catalyst, eg, acetamide or urea (24). Pyridine has also been used. Tertiary alcohols do not react. Reactions with phenols yield phenyl ammonium sulfates. These reactions iaclude those of naphthols, cresol, anisole, anethole, pyrocatechol, and hydroquinone. Ammonium aryl sulfates are formed as iatermediates and sulfonates are formed by subsequent rearrangement (25,26). 

Enamines from the Condensation of Aldehydes and Ketones with Secondary Amines. ... 

The most versatile method for preparing enamines involves the condensation of aldehydes and ketones with secondary amines [Eq. (1)]. Mannich and Davidsen (/) discovered that the reaction of secondary amines with aldehydes in the presence of potassium carbonate and at temperatures near 0° gave enamines, while calcium oxide and elevated temperatures were required to cause a reaction between ketones and secondary amines, although usually in poor yield. The introduction by Herr and Heyl 2-4) of the removal of the water produced in the condensation by azeotropic distillation with benzene made possible the facile preparation of enamines from ketones and disubstituted aldehydes. 

In a variation on this approach, p-chlorobenzaldehyde is rst condensed with 2-aminopyridine. Reduction of the resulting iff base (62) affords the corresponding secondary amine. Alkyl-ion with the usual side chain affords the antihistamine, chlor-ramine (64). ... 

The general features of this elegant and efficient synthesis are illustrated, in retrosynthetic format, in Scheme 4. Asteltoxin s structure presents several options for retrosynthetic simplification. Disassembly of asteltoxin in the manner illustrated in Scheme 4 furnishes intermediates 2-4. In the synthetic direction, attack on the aldehyde carbonyl in 2 by anion 3 (or its synthetic equivalent) would be expected to afford a secondary alcohol. After acid-catalyzed skeletal reorganization, the aldehydic function that terminates the doubly unsaturated side chain could then serve as the electrophile for an intermolecular aldol condensation with a-pyrone 4. Subsequent dehydration of the aldol adduct would then afford asteltoxin (1). 

In the case of tertiary N-ethylamine derivatives the N-ethyl group is first selectively oxidized by p-chloranil to an enamino group which then condenses with excess p-chloranil to a blue aminovinylquinone derivative [7]. Secondary N-ethyl derivatives do not yield blue aminovinylquinone derivatives they probably react directly with chloranil by nucleophihc attack at one of the four chlorine atoms to yield aminoquinones of other colors [7], It has also been suggested that some classes of substances react to yield charge transfer complexes [1, 5, 8, 12],... 

Sodium alkylamides can also be generated in situ by reacting the amine with sodium naphthalene in THF [207, 208]. This procedure has been used for the condensation of secondary amines with different 1,3-dienes to give high yields of monoalky-lated products without formation of 1 2 telomers. In the case of primary amines, mixtures of mono- and dialkylated products are obtained together with unidentified... 

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