Convenient access to functionalized vinylcyclopentenols from alkynyloxiranes

Beta,gamma-alkynyl aldehydes, generated in situ by treatment of alkynyloxiranes with a catalytic amount of Sc(OTf)3 or BF3.OEt2, are effectively trapped by a variety of allyl nucleophiles to afford homopropargylic homoallylic alcohols in good yield and selectivity. Such products are used as substrates for the synthesis of functionalized vinylcyclopentenols via enyne metathesis.     

Tosylated glycerol carbonate, a versatile bis-electrophile to access new functionalized glycidol derivatives

The reactivity of tosylated glycerol carbonate 2 toward nucleophiles has been exploited to generate glycidol analogues protected with carbonate or carbamate groups. The activated glycerol 2 is a reasonable linking agent with thiol and alcohol nucleophiles and an excellent and selective one with primary amines, allowing efficient bis-functionalizations of glycerol.     

A versatile and regiospecific synthesis of functionalized 1,3-diarylisobenzofurans

A convenient, versatile, and regiospecific synthesis of functionalized 1,3-diarylisobenzofurans has been developed. It involves chemoselective addition of arylmagnesium reagents to the aldehyde function of o-aroylbenzaldehydes, themselves readily obtained by lead tetraacetate oxidation of N-aroylhydrazones of salicylaldehydes. Various functional groups, including nitro, iodo, or ester functionalities, have thus been positioned with complete regiospecificity on the 1,3-diphenylisobenzofuran backbone.     

Convenient synthesis of highly functionalized pyrazolines via mild, photoactivated 1,3-dipolar cycloaddition

A mild, photoactivated 1,3-dipolar cycloaddition procedure was successfully developed for the synthesis of polysubstituted pyrazolines. This procedure involved the in situ generation of the reactive nitrile imine dipoles using a hand-held UV lamp at 302 nm, followed by spontaneous cycloaddition with a broad range of 1,3-dipolarophiles with excellent solvent compatibility, functional group tolerance, regioselectivity, and yield.     

Platinum-catalyzed tandem diboration/asymmetric allylboration: access to nonracemic functionalized 1,3-diols

[reaction: see text] A single-pot tandem catalytic diene diboration/carbonyl allylation reaction is described that uses a commercially available chiral diboron reagent. The chirality of the intermediate diboration adduct is transferred to the product in the carbonyl allylation reaction, thereby providing access to enantioenriched chiral products. Notably, the reaction allows for construction of a quaternary stereocenter and furnishes a synthetically versatile C-B bond in the reaction product.     

A Convenient One-Step Synthesis of 1,1,4,4-Tetrachloro-1,3-butadiene

During the course of our studies on selective chlorination by copper (II) chlorida¹ we considared it of intarest to tast the stability of the solvent commonly amployed by us – sulfolane– ⁺⁾ towards this haloganating agent.     

Synthesis of functionalized poly(1,3-dioxolane)

Classical initiation induces polymerization through cyclic tertiary oxonium ions which are responsible for the formation of an important quantity of cyclic oligomers. The activated monomer mechanism, i.e. polymerization in the presence of a diol, has been successful in the case of some substituted oxiranes such as epichlorohydrine and propylene oxide. It has also been used in the case of cyclic acetals [1,3-dioxolane (DXL) and 1,3-dioxepane (DXP)] and allows the preparation of dihydroxylated homopolymers as well as that of triblock copolymers. It was nevertheless shown that transacetalization leads to complications at the onset of the reaction. In order to shed some light on the reactions involved, we used a monoalcohol - methanol - instead of a diol. The products were separated and characterized: a monoadduct (methanol-DXL) was observed, confirming the occurence of the active monomer mechanism, but dimethoxymethane was also observed, evidence of transacetalization between methanol and DXL. It was shown that fast equilibration takes place between the following compounds: (methanol + DXL), (monoadduct of methanol and DXL), (dimethoxymethane + ethyleneglycol). When p-isopropenylbenzyl alcohol was used, it was possible to prepare macromonomers, i.e. poly(DXL) chains carrying polymerizable double bonds at their ends. Nevertheless because of the transacetalization reaction described above, a mixture of products was obtained.     

Convenient access to substituted acridines by a Buchwald-Hartwig amination

A convenient, high yield procedure for the synthesis of anthranilic acids carrying a variety of different substituents as well as their straightforward transformation into the corresponding 9-chloroacridines could be established by using modified Buchwald-Hartwig amination conditions.     

Convenient synthesis of functionalized terphenyls

A convenient synthetic methodology amenable for rapid synthesis of differentially functionalized terphenyls is described. Orthogonality requirements for the incorporation of phenoxy acetic acid and carboxamide function have been satisfied by utilization of hydroxyethoxy group as a precursor of the acid. Highly efficient and universal procedures have been developed for acid and amide formation.     

A versatile and highly stereoselective access to vinyl triflates derived from 1,3-dicarbonyl and related compounds

1,3-Dicarbonyl derivatives, such as 1,3-diketones, beta-ketoaldehydes, beta-ketoesters, beta-ketoamides, beta-ketophosphonates and beta-ketosulfones were efficiently converted to the corresponding Z vinyl triflates with high stereoselectivity. Precoordination with lithium triflate in dichloromethane and enolization with mild bases such as trialkylamines or DBU followed by trapping with triflic anhydride probably accounted for such high selectivity, achieved even at 0 degrees C. This method offers the first direct route to vinyl triflates from beta-ketoamides, beta-ketophosphonates and beta-ketosulfones.     

Asymmetric vinylogous Mannich reactions: a versatile approach to functionalized heterocycles

Asymmetric vinylogous Mannich reaction (VMR) of 2-(tert-butyldimethylsilyloxy)furan (TBSOF, 1) with (R(S))- or (S(S))-t-BS-imines (3) furnished 5-aminoalkylbutenolides 7a-k in 75-87% yields with anti/syn ratios ranging from 75:25 to 97:3. Butenolides 7a-f,k were readily converted into substituted lactones 8 and 5 and 6-substituted 5-hydroxypiperidin-2-ones 11a-g, which are, in turn, key intermediates for the synthesis of many bioactive compounds.     

Diels-Alder reactions of 1,3-dienylboronates as a new route to functionalized carbocycles.

Hydroboration of enynes with various hydroborating agents followed by refunctionalization at boron furnished 1,3-dienylboronates which undergo clean Diels-Alder addition to typical dienophiles. The resulting adducts contain an allylboronate functionality. Accordingly they add to aldehydes in a highly stereoselective fashion establishing the relative configuration at up to four stereogenic centers.     

Aziridinofullerene: a versatile platform for functionalized fullerenes

An aziridine moiety on the fullerene core can serve as an acid-triggered reacting template for the controlled synthesis of a range of functionalized fullerenes that are otherwise difficult to synthesize in an efficient and selective manner. A copper-catalyzed aziridination of C(60) for the practical synthesis of aziridinofullerene 1 and acid-catalyzed reactions of 1 with mono- and bifunctional nucleophiles as well as alkynes are described. The rapid generation of structural diversity in a single chemical operation using the common platform 1 is notable.     

Convenient access to bicyclic and tricyclic diazenes

Heating the tosylhydrazone of an omega-alkenyl ketone or aldehyde to reflux in toluene in the presence of K(2)CO(3) delivered the bicyclic diazene. Irradiation of the diazene converted it to the cyclopropane. This appears to be a generally useful method for the construction of substituted cyclopentanes and cyclohexanes.     

Facile conversion of cysteine and alkyl cysteines to dehydroalanine on protein surfaces: versatile and switchable access to functionalized proteins

An efficient and robust oxidative elimination of cysteine to dehydroalanine has been discovered. The reaction is induced by O-mesitylenesulfonylhydroxylamine (MSH) and is compatible with methionine. The key elimination has been executed on protein surfaces and allows ready access to different post-translationally modified proteins through conjugate addition of sulfur nucleophiles to dehydroalanine. Treatment of the resulting thioether with MSH results in regeneration of dehydroalanine, allowing a "functional switch" by subsequent addition of a different thiol.     

Convenient and versatile synthesis of formyl-substituted benzoxaboroles

Despite of the medicinal significance of benzoxaboroles, with the newly discovered clinical compound AN2690 as an example, the synthetic method for rapid diversification of this novel scaffold is lacking. To this end, a versatile and scalable synthesis of formyl-substituted benzoxaboroles is described here. A key step is the mono-oxidation of the two hydroxyls in compound 4 by taking advantage of the stable oxaborole ring in non-coordinating solvents, which was devised based on the study of the intramolecular coordination and exchange properties.     

Synthesis of functionalized organotrifluoroborates via the 1,3-dipolar cycloaddition of azides

[reaction: see text] We have successfully prepared potassium azidoalkyltrifluoroborates from the corresponding halogen compounds in 94-98% yields through a nucleophilic substitution reaction with NaN(3). In the presence of various alkynes and Cu(I) as a catalyst, these azidotrifluoroborates easily formed 1,4-disubstituted organo-[1,2,3]-triazol-1-yl-trifluoroborates in 85-98% yields. This method was then developed into a facile one-pot synthesis for the preparation of various organo-[1,2,3]-triazol-1-yl-trifluoroborates using haloalkyltrifluoroborates as the starting materials.