Sahcylaldehyde derivatives

Three studies related to the archetypal Stetter reaction have been reported. An asymmetric intramolecular version has been elaborated using sahcylaldehyde derivatives (124) as substrates and chiral triazolium salts (125) as precatalysts. Good levels of efficiency and enantioselectivity (up to 86% ee) have been obtained under the optimized reaction conditions. A similar novel triazolium salt (126) promotes the asymmetric intermolecular Stetter reaction of simple acrylates, which were previously considered to be unsuitable substrates. ... 

Reactions with Sahcylaldehydes. Tetraalkyl titanates react in benzene with sahcylaldehyde in a 1 1 or 1 2 molar ratio to give sahcylaldehydotrialkoxy and dialkoxy products, which when heated at reflux seem to undergo a Meewein-Pomidorf reaction to give an aldehyde derived from the alcohol group on the titanate and a reduced titanate complex (37) ... 

A family of interesting polycychc systems 106 related to pyrrolidines was obtained in a one-pot double intermolecular 1,3-dipolar cycloaddition, irradiating derivatives of o-allyl-sahcylaldehydes with microwaves in toluene for 10 min in presence of the TEA salt of glycine esters [71]. A very similar approach was previously proposed by Bashiardes and co-workers to obtain a one-pot multicomponent synthesis of benzopyrano-pyrrolidines 107 and pyrrole products 108 (Scheme 37). The latter cycloadducts were obtained when o-propargylic benzaldehydes were utihzed instead of o-allyhc benzalde-hydes, followed by in situ oxidation [72]. 

Dimeric oxovanadium(IV) complexes (NBu4)[(V0)(SB)]2- H20 have also been prepared with the SB from sahcylaldehyde and L, D,L-serine and L-cysteine. Magnetic moments are 1.1-1.4 BM, higher than for the dimeric SB derived from the L-amino acids Ala, Val, Leu, Met or Phe (0.5-0.8BM) which are probably best described as V complexes (114). ... 

Table 5 summarizes the reactions of isoprene with aromatic aldehydes and unsaturated aldehydes. Sahcylaldehyde provides the expected product as a cyclic boric ester derivative and shows apparently lower stereoselectivity, giving a mixture of 1,3-anti and, 3-syn isomers in a ratio of 6 1 (run 1, Table 5). 2-Furfural reacts as usual and provides a 1,3-anti isomer as a single diastereomer in good yield (run 2). Unsaturated aldehydes, irrespective of their substitution patterns, undergo homoallylation selectively with excellent 1,3-anti selectivity, the geometry of the double bond of the starting aldehydes remaining intact (runs 3-5). 1,2-Addition to unsaturated aldehyde takes place selectively and no 1,4-addition is observed.

Niefang, Y, Aramini, J.M., Germann, M.W., Huang, Z. 2000. Reactions of sahcylaldehydes with alkyl cyanoacetates on the surface of solid catalysts Syntheses of 4H-chromene derivatives. Tetrahedron Letters 41 6993-6996. 

Similar results were obtained by the reactions of zirconium alkoxide with salicylalde-hyde except that the rate of these reactions was faster and, unlike the titanium derivative, the product of the 1 2 molar reaction of Zr(OIV)4.IVOH with HOCeHjCHO (sahcylaldehyde) did not precipitate instead the product Zr2(0Pr )(0C6H4CH20)3 (OCeHrCHO) was directly obtained. 

Cyclocondensation of 2-hydroxybenzaldehydes (saHcylaldehydes) with reactive methylene compounds (malonic esters, cyanoacetic esters, malononitrile) in the presence of pyridine and other bases also leads - via lactonization of the primary condensation product 19 - to derivatives of coumarin-2-carboxylic acid 20 (Knoevenagel synthesis) ... 

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