5- Hydroxy-2-nitrobenzaldehyde

Hydroxy-2-nitrobenzaldehyde, 2688 4-Hydroxy-3-nitrobenzaldehyde, 2687 3 -Hydroxy-4-nitrobenzaldehyde, 2686... 

Epoxyquinomicin B (583), an antirheumatic agent, was synthesized in 22% overall yield in 8 steps starting from commercially available 3-hydroxy -nitrobenzaldehyde (584), which was easily converted to the amidophenol 585. Fremy s salt oxidation of 585 in Et0Ac-H20 was carried out at room temperature overnight to afford selectively in 82% yield the desired p-benzoquinone (586). This was treated with H202-NaHC03 in MeOH to yield the target molecule 583 (Scheme 109) . 

The AFO reaction has seen very few variations since it was first reported in 1934. However, the most significant modification was reported in 1958 by Ozawa and further elaborated by Smith and others. Prior to this modification the intermediate chalcones were purified and then subjected to hydrogen peroxide in a basic medium. With the modification, the chalcone was generated in situ, from an aldehyde and a hydroxyacetophenone, and then allowed to react with aqueous hydrogen peroxide in the presence of sodium hydroxide to deliver the flavonol. Smith and coworkers conducted a limited study to examine the scope and limitations of this modification.Flavonols were delivered in 51-67% however, no flavonols were isolated with highly reactive aldehydes such as p-nitrobenzaldehyde and when 2-hydroxy-4-methoxyacetophenone was used. 

This is by far the most versatile route to the synthesis of ester-substituted aziridines, especially as the benzhydryl group can easily be cleaved by hydrogenolysis. Wulff has applied this methodology to a short asymmetric synthesis of the antibiotic (-)-chloramphenicol in four steps from p-nitrobenzaldehyde (Scheme 1.34) [61]. In this case it was found that treatment of the aziridine 111 with excess dichloroacetic acid gave the hydroxy acetamide directly, so no separate deprotection step was required. 

A series of 11 nitrobenzaldehydes was examined by TGA, DSC and ARC techniques. Only 5-hydroxy-2-nitrobenzaldehyde decomposed exothermally in an unsealed container, but all did so in sealed capsules, under dynamic, isothermal or adiabatic conditions, with evolution of much gas. Initial decomposition temperatures in °C (compound, ARC value, and DSC value at lOVmin, respectively, followed by ARC energy of decomposition in kJ/g) were - 2-nitro-, 176, 220, 1.44 3-nitro-, 166, 218, 1.94 4-nitro-, 226, 260, 1.27 2-chloro-5-nitro-, 156, 226, 697 2-chloro-6-nitro-, 146, 220,. 832 4-chloro-3-nitro-, 116, 165, 1.42 5-chloro-2-nitro-, 240, 3-hydroxy-4-nitro-, 200, 4-hydroxy-3-nitro-, 200, 5-hydroxy-2-nitro-, 175, 3-methoxy-4-nitrobenzaldehyde, 245°C, -. 4-Nitrobenzaldehyde showed by... 

Derivatization of functional groups in a natural-product scaffold can also be effectively performed on the solid-phase. An example of this is the synthesis of a small compound collection (27-compounds) based on the tetrahydroquinoline scaffold. A chiral tetrahydroquinoline scaffold was synthesized in solution from 5-hydroxy-2-nitrobenzaldehyde (Scheme 4). The synthesis involved a key asymmetric aminohydroxylation step. This building block was anchored to the solid support with a Wang linker and diversity was introduced by selective deprotection and derivatization of the protected hydroxyl and amino substituents. 

At the same time, Snell and coworkers used model systems to achieve most of the reactions of the pyridoxal enzymes (Metzler and Snell, 1952a,b Olivard et al., 1952 Ikawa and Snell, 1954a,b Metzler et al 1954a,b Longnecker and Snell, 1957). They too developed the modern mechanisms for the series of reactions and demonstrated the role of the coenzyme as an electron sink by substituting alternative catalysts for pyridoxal phosphate. In particular, they showed that 2-hydroxy-4-nitrobenzaldehyde (Ikawa and Snell, 1954) functioned in their model systems just as did the vitamin its electronic structure is really quite similar (3). 

Treatment of the 2-oxopyrido[l,2-a]pyrimidine (22 R = H) with tri-ethyloxonium fluoroborate and subsequently with m-nitrobenzaldehyde gave the pyrido[l,2-a]pyrimidines(200). Hydrolysis of 200 with hydrochloric acid yielded 2-hydrazono-2/f-pyrido[l,2-a]pyrimidine following oxidative coupling with 1-hydroxy-2-napthanilide or 4-acetylaminodi-phenylamine, this was utilized for the preparation of azo dyes.252... 

Hydroxy-2-nitrobenzaldehyde, 2688 4-Hydroxy-3-nitrobenzenesulfonyl chloride, 2139 2-Hydroxy-6-nitro-1 -naphthalenediazonium-4-sulfonate, 3234 2-Hydroxy-2-phenylacetophenone, Benzoin, see 2-Hydroxy-1,2-diphenyletha-... 

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