Methanolic trimethylamine mediated Baylis-Hillman reaction

Application of methanolic trimethylamine, the tertiary amine containing minimum number of carbon atoms with lowest possible molecular weight, for mediating the Baylis-Hillman coupling of various aldehydes with activated olefins viz. methyl acrylate, acrylonitrile and acrolein is described

Silica grafted polyethylenimine as heterogeneous catalyst for condensation reactions

Primary amine groups were attached to a silica surface by using α,ω-diamines derivatives and (3-glycidyloxypropyl)-trimethoxysilane activation. The same activation was used to graft polyethylenimine, which also contains secondary and tertiary amine groups. These silica aminated structures were tested as heterogeneous catalysts in nitroaldol condensation with nitromethane, the derivative with the polyethylenimine moiety being the more active catalyst. This catalyst also showed efficiency in the Knoevenagel condensation of benzaldehydes with ethyl cyanoacetate under very mild reaction conditions and showed much the same efficiency when used in consecutive reaction runs. A reaction mechanism with participation of the several amine groups of the catalysts is discussed

Reactive organoallyl species generated from aryl halides and allene: allylation of alpha,beta-unsaturated aldehydes and cyclic ketones employing Pd/In transmetallation processes

Allylation of α,β-unsaturated aldehydes and cyclic ketones promoted by Pd/In transmetallation processes has been studied. The unsaturated aldehydes underwent regioselective 1,2-addition to afford secondary homoally alcohols. The reactions have been performed using Pd(OAc)2/PPh3 as catalytic system and metallic indium affording the products in good yields. The same transformation with unsaturated ketones proved to be less efficient, while saturated cyclic ketones delivered generally excellent yields in the presence of CuI. In these latter processes the presence of a distal heteroatom influences the reaction rate

Postpollination Changes in Floral Odor in Silene latifolia: Adaptive Mechanisms for Seed-Predator Avoidance?

Floral odor is a key trait for pollinator attraction in many plants, but may also direct antagonists like herbivores to flowers. In this study, we examined how floral scent changes after pollination in Silene latifolia, which has a specialized relationship with the seed predator Hadena bicruris. We found an overall decrease in total scent emission and considerable changes in relative amounts of scent compounds after pollination. Lilac aldehydes A and B as well as veratrole contributed most to the decrease in scent emission. These three compounds are known to be key signals for the attraction of H. bicruris to the flowers. A specific downregulation of these compounds may increase the reproductive success of the plant by reducing seed predation after pollinatio

Trimethylsilyl Trifluoromethanesulfonate- Accelerated Addition of Catalytically Generated Zinc Acetylides to Aldehydes

In the presence of TMSOTf, a wide variety of terminal acetylenes add rapidly and efficiently to aldehydes via a catalytically generated zinc acetylide. In the absence of TMSOTf, no reaction is observed under otherwise identical conditions

Kinetics and mechanism of protein tyrosine phosphatase 1B inactivation by acrolein

Human cells are exposed to the electrophilic [alpha],[beta]-unsaturated aldehyde acrolein from a variety of sources. The reaction of acrolein with functionally critical protein thiol residues can yield important biological consequences. Protein tyrosine phosphatases (PTPs) are an important class of cysteine-dependent enzymes whose reactivity with acrolein previously has not been well-characterized. These enzymes catalyze the dephosphorylation of phosphotyrosine residues on proteins via a phosphocysteine intermediate. PTPs work in tandem with protein tyrosine kinases to regulate a number of critically important mammalian signal transduction pathways. We find that acrolein is a potent time-dependent inactivator of the enzyme PTP1B (kinact = 0.02 [plus or minus] 0.005 s-1 and KI = 2.3 [plus or minus] 0.6 x 10-4 M). The enzyme activity does not return upon gel filtration of the inactivated enzyme, and addition of the competitive phosphatase inhibitor vanadate slows inactivation of PTP1B by acrolein. Together, these observations suggest that acrolein covalently modifies the active site of PTP1B. Mass spectrometric analysis reveals that acrolein modifies the catalytic cysteine residue at the active site of the enzyme. Aliphatic aldehydes such as glyoxal, acetaldehyde, and propanal are relatively weak inactivators of PTP1B under the conditions employed here. Similarly, unsaturated aldehydes such as crotonaldehyde and 3-methyl-2-butenal bearing substitution at the alkene terminus are poor inactivators of the enzyme. Overall, the data suggest that enzyme inactivation occurs via conjugate addition of the catalytic cysteine residue to the carbon-carbon double bond of acrolein. The results indicate that inactivation of PTPs should be considered as a possible contributor to the diverse biological activities of acrolein and structurally related α,β-unsaturated aldehydes

Highly chemoselective formation of aldehyde enamines under very mild reaction conditions

Abstract: Although ketone enamines are widely used in organic synthesis, aldehyde enamines are rarely employed due to the limitations of their preparation using known methods (need for acid or base, excess of amine, and/or elevated temperature). We have successfully developed rapid and particularly mild condensation conditions (1 h, 0 °C, 1.2 equiv of amine) leading to di- and trisubstituted enamines with excellent conversion (84−100%). Remarkably high chemoselectivity was observed with complete discrimination between aldehyde and ketone, among other functional groups positively tested

4(3<em>H</em>)-Quinazolinone Derivatives: Syntheses, Physical Properties, Chemical Reaction, and Biological Properties

4(3H)-Quinazolinone derivatives have considerable great interesting due to the diverse range of their biological properties. This review summarized the methods of preparation of 2-substituted-4(3H)-quinazolinone, 3-substituted-4(3H)-quinazolinone and 2,3-disubstituted-4(3H)-quinazolinone derivatives. Chemical reaction of 4(3H)-quinazolinone derivatives and the reactivity of the 2-methyl group, reactivity of the 3-amino group, electrophilic substitution, oxidation, reduction, reaction of 4(3H)-quinazolinones with metal ions, Mannich reaction, cycloaddition reaction as well as other reagents were discussed. Also, biological properties of 4(3H)-quinazolinone derivatives were given herein