[reaction: see text] Under standard hydroboration-oxidation conditions, the dihydropyrans 4 underwent a highly stereocontrolled tandem reaction, involving the expected hydration of the double bond together with the reduction of the ketal moiety. This unprecedented transformation gives rise to a short, [4 + 2]-based synthetic route to (+/-)-beta-C-naphthyl-2-deoxyglycosides 5, which allows a significant structural and functional diversity at C-6. We thus described the first synthesis of (+/-)-C-aryl-6-fluoro and -6,6-difluoro olivosides, via the allylic mono- and difluorides produced by regioselective fluorination of, respectively, hydroxyalkyl and oxoalkyl dihydropyran derivatives.

The synthesis of enantiopure bis-THF is described, starting from d-mannitol. Bis-THF is used as chiral ligand for organolithium reagents in four different reactions. The enantioselectivity provided by this ligand is moderate, and the asymmetric induction is in line with the expected model.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Regioisomerically pure trifluoromethyl- and trifluoromethoxy-substituted aromatic and heteroaromatic aldehydes and carboxylic acids are valuable building blocks for the synthesis of biologically active molecules. They have been prepared by employing modern organometallic methods. On this basis, a novel access to 2,3-dihydro-5-(trifluoromethoxy)indole was developed which represents an intriguing example of how organometallic and radical chemistry can fecundate each other.

The [4+2] heterocycloaddition reaction between (E)gamma-substituted beta-unsaturated alpha-oxo esters 1a-d and cyclic and acyclic ketone enol ethers 2a-1 afforded heteroadducts 3-5 in high yields when either [Eu(fod)(3)] or SnCl4 were used as the catalyst. With methyl (E)-benzylidenepyruvate (1a), the two catalytic modes displayed divergent stereoselectivities. In the case of the heterocycloaddition of silyl enol ether 2h, X-ray investigations established the relative configurations of the bicyclic adducts 3h and 5h, each obtained as the major isomer with [Eu(fod)3] and with SnCl4, respectively. These assignments provided valuable information concerning the concerted vs, nonconcerted mechanism of these acid-catalysed reactions, With methyl (E)-tert-butoxymethylenepyruvate (1d), the scope of the reaction proved to be restricted to alkyl enol ethers as the dienophiles. In this case, the stereochemical process followed a different pathway, exemplified by the X-ray structure of the adduct 4q, obtained with total stereoselectivity from 1d and 1-methoxycyclohexene (2f) when SnCl4 Was the catalyst.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Under Eu(fod)3-catalyzed conditions, the endo-selective hetero Diels–Alder reaction of (S)-(+)-O-vinyl mandelate with Wang-supported benzylidenepyruvate occurred with a 93/7 facial selectivity that compares well with those observed in solution. In addition, the solid-phase sequence allowed an unprecedented reuse of the catalyst in the presence of excess dienophile in solution.

A new and highly simple method for the synthesis of E-gamma -aryl-alpha -oxobutenoic esters is described. This unprecedented one-step procedure is based on an unexpected nucleophilic reactivity of alkyl pyruvates towards aromatic aldehydes in refluxing dichloromethane, when using catalytic amounts of Cu(OTf)(2) and in the presence of stoichiometric amounts of trimethyl orthoformate in the case of electron-rich aldehydes. Under these conditions, yields obtained are uniformly higher than those obtained by previous multistep procedures.

The OH groups of Wang resin were esterified with benzylidenepyruvic acid (1) to give the immobilized 1-oxabutadiene 2. The latter reacted with vinyl ethers 3a-h (dienophiles) in the presence of Eu(fod)(3), and the resulting adducts 4a-h underwent reductive cleavage with LiAlH4 to afford the dihydropyrans 5a-h in high (62 to 100%) overall yields. A similar sequence carried out under conventional homogeneous liquid phase conditions led to significantly lower yields. The endo/exo selectivity of the cycloaddition reaction was the same in both cases.