Lubineau reaction

Thermodynamic Knoevenagel condensation (Lubineau reaction) was applied to different carbohydrates, such as 2-acetamido sugars, fucose, lactose and various pentoses including, xylose, arabinose and S-deo) arabinose. ... 

When using acetoacetic esters as 1,3-dicarhonyl compounds in the presence of tertiary amine and 2-hydro g yridine as a dual catalyst, aldolisation adducts were obtained giving a simple access to carbon-elongated branched carbohydrates. This reaction was conducted at room temperature in DMSO no competitive Knovenagel condensation (Lubineau reaction) products were deteeted. 

These results differ considerably from those obtained by Lubineau reactions. In the Lubineau series, a Knoevenagel condensation followed by an oxa-Michael/intermolecular retro-Claisen process is proposed. As a result of the Lubineau sequence, the loss of an acetate-fragment occurs in reactions with acetylacetone. 

SCHEME 2.33 Comparison of amine-catalyzed cascade reaction with Lubineau reaction. 

Breslow studied the dimerisation of cyclopentadiene and the reaction between substituted maleimides and 9-(hydroxymethyl)anthracene in alcohol-water mixtures. He successfully correlated the rate constant with the solubility of the starting materials for each Diels-Alder reaction. From these relations he estimated the change in solvent accessible surface between initial state and activated complex " . Again, Breslow completely neglects hydrogen bonding interactions, but since he only studied alcohol-water mixtures, the enforced hydrophobic interactions will dominate the behaviour. Recently, also Diels-Alder reactions in dilute salt solutions in aqueous ethanol have been studied and minor rate increases have been observed Lubineau has demonstrated that addition of sugars can induce an extra acceleration of the aqueous Diels-Alder reaction . Also the effect of surfactants on Diels-Alder reactions has been studied. This topic will be extensively reviewed in Chapter 4. 

The extensive work of Lubineau further demonstrated the merits of water with respect to the rates and selectivities of the Diels-Alder reaction. Since 1985 he has published a large number of articles dealirig mainly with dienes that were rendered water soluble through the temporary introduction of a... 

A combination of the promoting effects of Lewis acids and water is a logical next step. However, to say the least, water has not been a very popular medium for Lewis-acid catalysed Diels-Alder reactions, which is not surprising since water molecules interact strongly with Lewis-acidic and the Lewis-basic atoms of the reacting system. In 1994, when the research described in this thesis was initiated, only one example of Lewis-acid catalysis of a Diels-Alder reaction in water was published Lubineau and co-workers employed lanthanide triflates as a catalyst for the Diels-Alder reaction of glyoxylate to a relatively unreactive diene . No comparison was made between the process in water and in organic solvents. 

Lubineau and coworkers [18] have shown that glyoxal 8 (Ri = R2 = H), glyoxylic acid 8 (Ri = H, R2 = OH), pyruvic acid 8 (Ri = Me, R2 = OH) and pyruvaldehyde 8 (Ri = H, R2 = Me) give Diels-Alder reactions in water with poor reactive dienes, although these dienophiles are, for the most part, in the hydrated form. Scheme 6.6 illustrates the reactions with (E)-1,3-dimethyl-butadiene. The reaction yields are generally good and the ratio of adducts 9 and 10 reflects the thermodynamic control of the reaction. In organic solvent, the reaction is kinetically controlled and the diastereoselectivity is reversed. 

Armentrout PB (2003) Threshold Collision-Induced Dissociations for the Determination of Accurate Gas-Phase Binding Energies and Reaction Barriers. 225 227-256 Astruc D, Blais J-C, Cloutet E, Djakovitch L, Rigaut S, Ruiz J, Sartor V, Valerio C (2000) The First Organometallic Dendrimers Design and Redox Functions. 210 229-259 Aug6 J, see Lubineau A (1999) 206 1-39... 

The thermo- and photocycloaddition of alkenes will be discussed in Chapter 12, on pericyclic reactions. On the other hand, transition-metals have effectively catalyzed some synthetically useful cycloaddition reactions in water. For example, Lubineau and co-worker reported a [4 + 3] cycloaddition by reacting a,a-dibromo ketones with furan or cyclopen-tadiene mediated by iron or copper, or a-chloro ketones in the presence of triethylamine (Eq. 3.48).185... 

The crossed aldol reaction of silyl enol ethers with carbonyl compounds (Mukaiyama-aldol) was studied by Lubineau and co-workers... 

A significant acceleration of Michael addition was reported by Lubineau in the reaction of nitroalkanes with buten-2-one when the reaction media was changed from nonpolar organic solvents to water... 

Acyclic dienes react with glyoxylic acid via an oxo-Diels-Alder reaction to give dihydropyran derivatives (Eq. 12.53). An excellent application of the oxo-Diels-Alder reaction is reported by Lubineau et al. in the synthesis of the sialic acids, 3-deoxy-Z)-manno-2-octulosonic acid (KDO) and 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN).123... 

Lubineau A,Aug6 J (1999) Water as Solvent in Organic Synthesis. 206 1-39 Loupy A (1999) Solvent-Free Reactions. 206 153-207 March NH (1999) Localization via Density Functionals. 203 201-230 Maul J J, Ostrowski PJ, Ublacker GA, Linclau B, Curran DP (1999) Benzotrifluoride and Derivates Useful Solvents for Organic Synthesis and Fluorous Synthesis. 206 79-105 McDonnell KA, see Imperial B (1999) 202 1-38... 

Researchers of L Oreal confirmed the results obtained by Lubineau s group and applied the reaction to other sugars such as o-xylose (7), o-lactose (51), o-fucose (52), D-arabinose (8), and 3-deoxy-D-arabinose (53) [115] (Fig. 8). 

Other nucleophilic additions conducted in aqueous media can be found in the literature (Lubineau et al., 1994 Strauss, 1999). These reactions will include the benzoin condensation, the Prins reaction, and the Wittig-Horner reaction, and the Baeyer-Villi-ger oxidation. 

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