Benzaldehyde biological activities

In his approach toward selenium-containing heterocycles with potential biological activity, Abdel-Hafez reacted 2-amino-3-(4,5-dihydro-17/-imidazol-2-yl)-4,5,6,7-tetrahydro-l-benzoselenophene 297 with triethyl orthoformate and benzaldehyde to generate the tricyclic systems 296 and 298, respectively (Scheme 21) <2005RJ0396>. Similarly, reaction with carbon disulfide gave the corresponding thiourea 299. 

A recent extension of this methodology includes condensation of 44 with a variety of substituted benzaldehydes, furfurals, and thiophene carboxaldehydes afforded analogues of 48 in good to excellent yield as shown in Table 6.2 (Fig. 6.6). These products were completely characterized spectroscopically with an excellent discussion of the effects of substituents on the corresponding UV, IR, MS, and NMR spectra. Neutralization of 48 with sodium bicarbonate in aqueous ethanol produced the corresponding free bases uneventfully. These compounds were evaluated both as cyanine dyes and for biological activity. Condensation of 44 with ( )-3-(5-methylfuran-2-yl)-2-propenal affords the expected E, )-dienes 49a and 49b in 50 and 90% yield, respectively (Fig. 6.7). 

Carboxy-functionalized fluorescein dyes are important as conjugated fluorescent markers of biologically active compounds. M.H. Lyttle et al. have used the Dakin oxidation on 4-methoxy-3-hydroxy-2-chloro-benzaldehyde to obtain the desired resorcinol derivative that served as an intermediate in their improved synthesis. ... 

Indole and its derivatives have versatile biological activities and found in various biologically active natural products. Chakraborti and coworkers reported the catalytic applications of various room-temperature ionic liquids (RTILs) during the reaction of aldehydes with indole under solvent-free conditions for the synthesis of bis(indolyl)methanes. The reaction of indole with benzaldehyde under neat conditions and at room temperature was considered for a model study (Fig. 12.31). 

Isoquinoline derivatives are an important family of natural products. They have diverse biological activities and are used, for example, as bronchodi-lators, skeletal muscle relaxants, and antiseptics. The solid-phase synthesis of a 43,000-compound tetrahydroisoquinoline 2 combinatorial library has been reported by Griffith et al. [32]. The library was synthesized by a three-step procedure. An imine was formed by reacting a substituted benzaldehyde with a methylbenzhydrylamine (MB HA) resin-bound amino acid. Imine formation was driven to completion using trimethylorthoformate as a dehydrating reagent. Treatment of the imine with homophthalic anhydride provided the desired tetrahydroisoquinoline (Fig. 3a). 

Amines are a group of biologically active and even toxic compounds that cause environmental problems in agriculture, water, food, and medicines [19]. It was first showed by Saito et al. that CuPc layer has sensitivity to 100 ppm in the vapor of trithylamine and benzaldehyde by monitoring changes in the electric resistance [53]. The response time is short for triethylamine. The relationship between degree of response and concentration is shown in Figure 3.6. 

Reductions of aromatic nitro compounds provide a simple and general access to various heterocyclic compounds through the domino process (Scheme 9.23). Quinolines are important skeletal moieties present in various natural products and biologically active compounds [58]. Most common methods of their preparation involve condensation of o-amino benzaldehydes with an enolizable carbonyl compound (Friedlander synthesis) [59]. Miller et al. [60] reported an efficient synthesis of quinolines 109, in which a reduction of o-nitroaryl carbaldehyde by SnCl2 followed by condensation with an enolizable carbonyl compound in the presence of ZnCl2 yielded 109 through a domino process. In 2001, Bunce et al. [61] reported a domino nitroarene reduction/reductive amination sequence for the preparation of tetrahydroquinoline-4-carboxylic ester 110 with excellent yields. 

Gold-catalyzed annulations of 2-alkynyl benzaldehydes with dihydrofurans afforded a bicyclo[2.2.2]octane. These products contain interesting substructures that have been found in many biologically active molecules and natural products (13CEJ4043). 

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