Aldehyde and ring

Sulphamide annulates adjacent aldehyde and ring ketone groups in the presence of a strong base. 

FIGURE 8-3 Conformations of ribose. (a) In solution, the straight-chain (aldehyde) and ring (/3-furanose) forms of free ribose are in equilibrium. RNA contains only the ring form, /3-D-ribofuranose. Deoxy-ribose undergoes a similar interconversion in solution, but in DNA exists solely as /3-2 -deoxy-o-ribofuranose. (b) Ribofuranose rings in nucleotides can exist in four different puckered conformations. In all cases, four of the five atoms are in a single plane. The fifth atom (C-2 or C-3 j is on either the same (endo) or the opposite (exo) side of the plane relative to the C-5 atom. 

As base. Numerous reactions that are initiated by deprotonation have been conducted with KF-AI2O3. These include the synthesis of diaryl ethers, amines, and sulfides by nucleophilic aromatic substitutions, AJ-alkylation of 2,4-dinitrophenyl-hydrazones, condensation of 3-phenylisoxazol-5-one with aldehydes, and ring closure of /V-(w-chloroalkyl) carboxamides to afford 1,3-oxazolines and 1,3-oxazines. ... 

The decomposition of a glycidic ester to an aldehyde and carbon dioxide may involve the formation of a quasi six-membered ring, followed by the shift of three electron pairs ... 

The reaction probably must involve two steps, aldolization followed by crotonisation. and depends among other factors on the specific reactivity of the aldehyde and of the methyl, which is influenced both by the nature of the substituents on the ring and bv the nature of the anion (Scheme 35) (57. 58. 657)... 

The formation of pyridine derivatives from a, P-unsaturated aldehydes and ammonia involves formation of three bonds during the ring synthesis. For example, with an a, P-unsaturated aldehyde, both 2,5-substituted as well as 3,4-substituted pyridines can be obtained, depending on whether a 1,2- (eq. 17) or 1,4-addition (eq. 18) occurs with ammonia. Reactions are performed in the vapor phase with catalysts. 

Pyridazine aldehydes and ketones with the carbonyl group at the ring or in a side chain react in the usual manner. They form hydrazones, semicarbazides, oximes, etc. Side-chain aldehydes can be easily oxidized to pyridazinecarboxylic acids with silver nitrate and side-chain ketones are oxidized to carboxylic acids by treatment with potassium permanganate or hydrogen peroxide. 

Chloral forms well-crystallized adducts (126) with diaziridines containing at least one NH group (B-67MI50800). Carbonyl addition products to formaldehyde or cyclohexanone were also described. Mixtures of aldehydes and ammonia react with unsubstituted diaziridines with formation of a triazolidine ring (128). Fused diaziridines like (128) are always obtained in ring synthesis of diaziridines (127) from aldehyde, ammonia and chloramine. The existence of three stereoisomers of compounds (128) was demonstrated (76JOC3221). Diaziridines form Mannich bases with morpholine and formaldehyde (64JMC626), e.g. (129). 

Tetrahydroharman, m.p. 179-80°, has been prepared by a number of workers by a modification of this reaction, viz., by the interaction of tryptamine (3-)5-aminoethylindole) with acetaldehyde or paraldehyde and Hahn et al. have obtained a series of derivatives of tetrahydronorharman by the use of other aldehydes and a-ketonic acids under biological conditions of pH and temperature, while Asahina and Osada, by the action of aromatic acid chlorides on the same amine, have prepared a series of amides from which the corresponding substituted dihydronorharmans have been made by effecting ring closure with phosphorus pentoxide in xylene solution. 

If a molecule contains both a ketonic and aldehydic carbonyl group, a secondary amine will react with the aldehydic carbonyl group to give a -enamino ketone (15). This has been shown not only for 2-formylcyclo-hexanone (14) (32,33) but also in steroidal systems when the aldehyde and ketone groups are in five- or six-membered rings (34). 

The condensation of sulfonyl chlorides with enamines (452,453) derived from aldehydes and ketones has led to four-membered-ring sulfones, presumably through such intermediates (454-464). Open sulfonation products have also been obtained, particularly from ketone-derived enamines and from a-disubstituted sulfonyl chlorides. 

In general, imines are too reactive to be used to protect carbonyl groups. In a synthesis of juncusol, however, a bromo- and an iodocyclobexylbnine of two identical aromatic aldehydes were coupled by an Ullmann coupling reaction modified by Ziegler. The imines were cleaved by acidic hydrolysis (aq. oxalic acid, THE, 20°, 1 h, 95% yield). Imines of aromatic aldehydes have also been prepared to protect the aldehyde during ring metalation with. -BuLi. ... 

The hydrochloride of (3) holds water rather tenaciously, and the infrared spectrum indicates that the water is covalently bound. Mild oxidation of the cation (3) gives 4-hydroxyquinazoline in high yield and ring-chain tautomerism is excluded on the grounds that quinazo-line does not give a positive aldehyde test in acid solution, 2-Methyl-quinazoline also has an anomalous cationic spectrum and a high basic strength (see Table I), but 2,4-dimethylquinazoline is normal in both these respects, which supports the view that abnormal cation formation entails attack on an unsubstituted 4-position. ... 

Heating the mesoionic l-amino-2-thioxo-l,2,4-triazolo[l,5-c]quinazo-lines 59 with aromatic aldehydes and ethanolic hydrochloric acid resulted in the formation of Schiff bases and simultaneous pyrimidine ring cleavage... 

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