A novel stereoselective one-pot conversion of alcohols into alkyl halides mediated by N,N'-diisopropylcarbodiimide

Alcohols can be converted in high yields to the corresponding alkyl halides in a one-pot procedure via the corresponding O-alkylisourea; very short reaction times are possible when microwave irradiation is used.     

Efficient, highly regioselective, and stereospecific conversion of glycidol systems into C2-O-acylated vicinal halohydrins

Glycidyl esters and ethers undergo a regioselective and stereospecific opening of the oxirane ring upon treatment in chloroform in the presence of pyridine with trimethylsilyl halide (TMSX, X = Cl, Br, or I) and a mixture of carboxylic acid (CA)-trifluoroacetic anhydride (TFAA), to produce the corresponding C2-O-acylated vicinal halohydrins in high yields.     

A facile synthesis of 1,2-oxaphospholenes and stereoselective conversion into oxaphospholanes

Treatment of α-acylallylphosphonates with m-CPBA in the presence of MgSO₄, afforded 1,2-oxaphosphol-3-enes 2-oxides and the subsequent cuprate addition produced 1,2-oxaphospholanes stereoselectively.     

A general,highly stereoselective synthesis of amines

The stereochemical course of cycloalkanone imine reductions by a variety of boron hydride reagents is described; very high stereoselectivity with substituted alkali metal borohydrides is reported.     

On the stereospecific conversion of proximally-oxygenated trisubstituted vinyltriphenylstannanes into stereodefined trisubstituted alkenes

[reaction: see text] Allylically oxygenated vinyl alpha-triphenylstannanes such as 22 can be readily converted into vinyl iodides and thereafter stereodefined trisubstituted alkenes with retention of configuration.     

Metal-free one-pot oxidative conversion of benzylic alcohols and benzylic halides into aromatic amides with molecular iodine in aq ammonia, and hydrogen peroxide

Various primary alcohols, particularly benzylic alcohols, could be converted into the corresponding aromatic amides in good yields in a one-pot manner by treatment with molecular iodine in aq. NH₃, followed by reaction with ∼30% aq H₂O₂. Similarly, various benzylic halides could be also converted into the corresponding aromatic amides in good yields in a one-pot manner by treatment with molecular iodine in aq NH₃, followed by reaction with ∼30% aq H₂O₂. The present reactions involve the metal-free one-pot oxidative conversion of benzylic alcohols and benzylic halides into the corresponding aromatic amides, respectively.     

One-step stereospecific conversion of alcohols into dithiocarbamates: A smooth pathway for the introduction of a sulphur functionality

Functionnally diverse dithiocarbamates were prepared from the corresponding alcohols in a mild high-yielding one-pot synthesis involving unexpensive ziram (zinc N,N-dimethyldlthio carbamate) in a stereospecific Mitsunobu type procedure.     

A highly enantioselective phosphabicyclooctane catalyst for the kinetic resolution of benzylic alcohols

A new class of chiral phosphines belonging to the P-aryl-2-phosphabicyclo[3.3.0]octane family (PBO) has been prepared by enantioselective synthesis starting from lactate esters and 2,2-dimethylcyclopentanone enolate 5. A selective enolate alkylation method has been developed for preparation of 9 and 10 using a chelating ester substituent in the triflate alkylating agent 11. Subsequent conversion to the PBO catalysts 2 and 39 relies on a diastereoselective cyclization from the cyclic sulfate 17 and LiPHAr to afford the more hindered endo-aryl phosphines. These phosphines function as efficient catalysts for the kinetic resolutions of aryl alkyl carbinols by benzoylation (16, 21, 22) or iso-butyroylation in the case of the less hindered aryl alkyl carbinol substrates. With o-substituted aryl alkyl carbinols, the enantioselectivities exceed 100, and s = 380 +/- 10 has been demonstrated in the case of methyl mesityl carbinol. The PBO-catalyzed acylations probably involve a P-acylphosphonium carboxylate intermediate and a tightly ion paired transition state.     

A simple, efficient alternative for highly stereoselective iodoacetoxylation of protected glycals

Protected glycals are converted in high yields and selectivities in less than 2 h at low temperatures to 2-deoxy-2-iodoglycosyl acetates using the simple, inexpensive reagent mixture of ammonium iodide, hydrogen peroxide and acetic anhydride/acetic acid in acetonitrile. The corresponding 2-deoxy-2-bromoglycosyl acetates are obtained using ammonium bromide instead of the iodide, although longer reaction times are required and selectivities are inferior.     

A non-iterative, flexible, and highly stereoselective synthesis of polydeoxypropionates--synthesis of (+)-vittatalactone

A short sequence comprising an oxy-Cope rearrangement, iridium-catalyzed hydrogenation, and enolate methylation provides trideoxypropionates with excellent diastereocontrol. A straightforward synthesis of the cucumber beetle pheromone (+)-vittatalactone illustrates this new strategy.     

Palladium-catalyzed conversion of benzylic and allylic halides into alpha-aryl and beta,gamma-unsaturated tertiary amides by the use of a carbamoylsilane

[reaction: see text] Treatment of allylic and benzylic halides with N,N-dimethylcarbamoyl(trimethyl)silane in the presence of tetrakis(triphenylphosphine)palladium(0) affords tertiary amides, which arise from the replacement of the halogen by the N,N-dimethylcarbamoyl group.     

Sodium iodide/boron trifluoride etherate: A mild reagent system for the conversion of allylic and benzylic alcohols into corresponding iodides and sulfoxides into sulfides

A variety of allylic and benzylic alcohols have been converted into the corresponding iodides using NaI/BF₃.Et₂O. Selective conversion of allylic and benzylic alcohols in preference to primary saturated alcohols has also been demonstrated. Further, the same reagent system has been used to convert sulfoxides into sulfides under mild conditions.     

A very simple, highly stereoselective and modular synthesis of ferrocene-based P-chiral phosphine ligands

A very simple, highly stereoselective and modular synthesis of ferrocene-based P-chiral phosphine ligands has been developed. On the basis of this new methodology, several new families of ferrocene-based phosphine ligands have been prepared coupling chirality at phosphorus with other, more standard stereogenic features. The introduction of P-chirality into ferrocene-based phosphine ligands enhances the enantioselective discrimination produced by the corresponding Rh catalyst when a matching among the planar chirality, carbon chirality, and the chirality of phosphorus is achieved.     

A highly stereospecific synthesis of (E)-α,β-unsaturated esters

CrCl₂-induced olefination of aldehydes using methyl dichloroacetate exclusively generates (E)-α,β-unsaturated esters in excellent yields. The intermediate α-chloro-β-hydroxy adducts could also be isolated in good yields under conditions of limited reagent.