Aldehydes bromo

Commercially available 2-ethylhexanal (Eastman practical grade) is purified by fractional distillation b.p. 163-163.2°/atm., no 1.4133. Other aldehydes are conveniently prepared by the Rosenmund reduction.2 If the aldehyde is relatively unstable toward autoxidation,3 a catalytic amount (0.5-1.0 g.) of hydroquinone is added with the aldehyde-bromo ester solution. 

Reformatski reaction Aldehydes and ketones react with a-bromo- fatty acid esters in the presence of zinc powder to give -hydroxy-esters which may be dehydrated to give a-, 0-unsaturated esters. a-Chloroesters will react if copper powder is used in conjunction with the zinc. 

The reaction of a-bromo (or a-chloro) aldehydes with higher... 

Cl or Br designates the corresponding a-ch1oro- or a-bromo-aldehyde or ketone. 

Thiophene-2-carbaldehyde, 3-bromo-synthesis, 4, 81 Thiophenecarbaldehydes benzothiophene synthesis from, 4, 906 reactions, 4, 807 synthesis, 4, 148 Wittig reactions, 4, 807 Thiophene-2-carb aldehydes bromination, 4, 753 conformation, 4, 33 halogenation, 4, 753 reactions, 4, 72-73 reactivity, 4, 72-73 reduction, 4, 776 Thiophene-3-carb aldehydes conformation, 4, 33 reactivity, 4, 72... 

In general, imines are too reactive to be used to protect carbonyl groups. In a synthesis of juncusol, however, a bromo- and an iodocyclohexylimine of two identical aromatic aldehydes were coupled by an Ullman coupling reaction modi-fied by Ziegler. The imines were cleaved by acidic hydrolysis (aq. oxalic acid, THF, 20°, 1 h, 95% yield). Imines of aromatic aldehydes have also been prepared... 

The conversion of the intermediate bromo aldehyde to the dioxane proceeds readily owing to a favorable equilibrium position. However, the equilibrium for the reaction of the bromo ketone with the diol is unfavorable and requires removal of the by-product, water. This is done under mild conditions using... 

Base-catalyzed fragmentation also occurs on treatment of 5,6j9-epoxy-19-aldehyde (hemiacetal, hemiacetal-acetate or 3)5,6/ -acetal) accessible from nitrous acid-acetic acid treatment of 5a-bromo-6jS-hydroxy-19-oximes followed by mild base hydrolysis (yield not reported)... 

The halogenation of enamines is formally analogous to protonation with salt formation. Thus the steroidal enamine (164) undergoes bromination (7/5) to give the j8-bromo iminium bromide (165), which is readily hydrolyzed to the /5-bromo aldehyde (166). 

From resonance structure (12) it is obvious that a —I—M-substit-uent strongly deactivates the 2-position toward electrophilic substitution, and one would thus expect that monosubstitution occurs exclusively in the 5-position. This has also been found to be the case in the chlorination, bromination, and nitration of 3-thiophenecarboxylic acid. Upon chlorination and bromination a second halogen could be introduced in the 2-position, although further nitration of 5-nitro-3-thiopheneearboxylic acid could not be achieved. Similarly, 3-thiophene aldehyde has been nitrated to 5-nitro-3-thiophene aldehyde, and it is further claimed that 5-bromo-3-thiopheneboronic acid is obtained upon bromination of 3-thiopheneboronic acid. ... 

Under conditions more similar to those of the Reimer-Tiemann reaction 3-bromopyridine was obtained from pyrrole and bromo-form. Treatment of pyrrole with chloroform and aqueous alkali gave pyrrole-2-aldehyde curiously, the formation of 3-chloropyridine under these conditions does not appear to have been reported, in spite of being frequently quoted. However, indole gave both indole-3-aldehyde and 3-chloroquinoline under these conditions [Eq. (10)]. 

Isothiazole-3-carboxylic acid and its 4-bromo derivative have been obtained by oxidation of the corresponding aldehydes with silver oxide. They form acid chlorides, esters, and amides. The amides may be dehydrated to give the corresponding nitriles. ... 

Kitazume and Kasai [55] have investigated the Reformatsky reaction in three ionic liquids. This reaction involves treatment of an a-bromo ester with zinc to give an a-zinc bromide ester, which in turn reacts with an aldehyde to give an addition product. An example is given in Scheme 5.1-26. Moderate to good yields (45-95 %) were obtained in ionic liquids such as [EDBU][OTf] for the reactions between ethyl bro-moacetate or ethyl bromodifluoroacetate and benzaldehyde [55]. 

It was decided to construct a D-ring acylating agent bearing a latent C-8 vinyl group. To this end, benzylation of the known 5-bromo-orr/to-vanillin (22),14 followed by protection of the aldehyde carbonyl in the form of a cyclic acetal (1,3-dioxane), affords com-... 

A mixture of 1- and 3-chloro, 1,3-dichloro, and 1,3,5-trichloro derivatives was obtained on chlorination of imidazo[l, 5-a]pyrazine (172). Bromination gave similar results (75JHC207,75JOC3373 84MI24). The 8-chloro compound is best made from the 8-oxy derivative of 172. When the 1-bromo-3-methyl derivative of 172 was treated in turn with aqueous bromine and excess dilute caustic soda, the pyrazine ring was destroyed to give 4-bromo-2-methylimidazole-5-aldehyde (75JOC3373). 

Finally, 2-allyl-4,5-tra ,s-diphenyl-l,3-bis(4-methylphenylsulfonyl)-l,3,2-diazaborolidincs have been used74. The 2-propenyl derivative undergoes highly stereoselective reactions with achiral aldehydes (95 - 97% ee) the ( )-2-butenyl derivatives (91-95% ee) and the analogous 2-chloro- and 2-bromo-2-propenyl derivatives (84-99% ee) also give excellent results in reactions with achiral aldehydes. 

The addition of the 2-butenylchromium reagent to achiral aldehydes proceeds with excellent anti selectivity, irrespective of whether (E)- or (Z)-l-bromo-2-butene is used as precursor. 

Bromo-2-phenylsulfonyl-2-butene adds with syn selectivity to aldehydes indicating again that in the intermediate chromium species the 3-alkyl group is forced to occupy the position trims to the bulky 2-substituent20,21. 

In the condensation reaction between chloro- and bromo-methyl aryl sulfones and carbonyl compounds, a-sulfonyloxiranes were obtained. In this condensation reaction, bases such as potassium t-butoxides372, NaH373 and aqueous concentrated hydroxide with benzyltriethylammonium chloride under two-phase condensation were used374. In the reaction with aldehydes only the trans-epoxide isomers resulted, whereas lith-iofluoromethyl phenyl sulfone 289375 and 291376 were found to add to aldehydes affording /J-hydroxysulfones 290 and 292, respectively. 

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