Isidro M. Pastor

Transition-Metal-Catalyzed Synthesis of Hydroxylated Arenes

An overview of the recent bibliography in the transition-metal-catalyzed hydroxylation of aryl derivatives is presented. Two reaction protocols are considered: 1) C--H activation/hydroxylation and, 2) cross-coupling hydroxylation of aryl halides. The achievements and limitations for both procedures are described taking into consideration different metal catalyst/oxidant combinations.

Asymmetric Ring Opening of Epoxides

This review deals with the metal promoted asymmetric ring opening of achiral epoxides using achiral carbon-, nitrogen-, oxygen-, sulphur- and halogen-containing nucleophiles. The use of chiral bases in the asymmetric deprotonation of achiral epoxides yields chiral allylic alcohols. Finally, kinetic resolution of racemic epoxides can be achieved using chiral metal complexes.

Novel simple and highly modular ligands for efficient asymmetric transfer-hydrogenation of ketones

Novel simple and highly modular dipeptide-analogue ligands combined with [RuCl2(p-cymene)]2 were demonstrated to efficiently catalyze the reduction of ketones under hydrogen transfer conditions with enantioselectivities up to 96%.

Novel highly modular C2-symmetric oxazoline ligands—application in titanium-catalyzed diethylzinc additions to aldehydes

Abstract Novel C 2 -symmetric tetradentate bis-oxazoline ligands were efficiently prepared from α-amino acids, 1,2-amino alcohols and 1,2- or 1,3-diacids. The ligands were employed in the titanium-catalyzed addition of diethylzinc to benzaldehyde, and depending on conditions used, moderate to high enantioselectivities of the formed 1-phenylpropanol were obtained.

Recent Advances in Asymmetric Organocatalyzed Conjugate Additions to Nitroalkenes

The asymmetric conjugate addition of carbon and heteroatom nucleophiles to nitroalkenes is a very interesting tool for the construction of highly functionalized synthetic building blocks. Thanks to the rapid development of asymmetric organocatalysis, significant progress has been made during the last years in achieving efficiently this process, concerning chiral organocatalysts, substrates and reaction conditions. This review surveys the advances in asymmetric organocatalytic conjugate addition reactions to α,β-unsaturated nitroalkenes developed between 2013 and early 2017.

New reactivity of functionalised organolithium compounds in the presence of Cu(I) or Cu(II) salts: conjugate addition, acylation or dimerisation

Abstract The reaction of functionalised organolithium compounds 1 with electrophilic olefins 2 in the presence of copper(I) iodide and HMPA in THF at −78°C leads, after hydrolysis with a saturated solution of ammonium chloride, to the corresponding products 3 resulting from a conjugate addition. The same process but using an acyl chloride instead of the electrophilic olefins affords the expected ketone 4 from an acylation process. Finally, when intermediates 1 are treated with copper(II) chloride in THF at −78°C, the corresponding dimers 5 are isolated after the same hydrolytic treatment.

Copper(I) or (II)-mediated conjugate addition or dimerisation of functionalised organolithium compounds

Abstract The reaction of different functionalised organolithium intermediates 1 – 3 with several electrophilic olefins 6 (2-cyclopentenone, 2-cyclohexenone, methyl vinyl ketone, benzylideneacetone, benzylideneacetophenone and ethyl acrylate) in the presence of copper(I) salts (bromide and iodide) in THF at −78°C gives, after hydrolysis with ammonium chloride, the expected products resulting from a conjugate addition. In the presence of copper(II) chloride intermediates 1 – 5 undergo dimerisation to yield the expected dimers.

Palladium and Organocatalysis: An Excellent Recipe for Asymmetric Synthesis

The dual activation of simple substrates by the combination of organocatalysis and palladium catalysis has been successfully applied in a variety of different asymmetric transformations. Thus, the asymmetric α-allylation of carbonyl compounds, α-fluorination of acyl derivatives, decarboxylative protonation of β-dicarbonyl compounds, cyclization reactions of alkynyl carbonyl compounds and β-functionalization of aldehydes have been efficiently achieved employing this double-catalytic methodology.

Lithium- α-lithioacetate and β-lithiopropionate: useful intermediates in organic synthesis

The reaction of chloroacetic acid and 3-chloropropionic acid with a base (LDA or BunLi, respectively) and then with an excess of lithium and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5%) in the presence of different electrophiles [ButCHO, PhCHO, Et2CO, (CH2)5CO, PhCOMe] in THF at −78°C leads, after hydrolysis with water, to the expected hydroxy acids, which in the second case are directly cyclised under acidic conditions to give the expected γ-lactones.

Masked β-, γ- and δ-lithium ester enolates: useful reagents in organic synthesis

Abstract The reaction of ω-chloro orthoesters 1 with lithium and a catalytic amount of 4,4′-di- tert -butylbiphenyl (DTBB, 5% molar) in the presence of different electrophiles [Bu t CHO, PhCHO, (CH 2 ) 5 CO, Et 2 CO, PhCOMe, PhCH NPh, Me 3 SiCl] in THF at −78°C leads, after hydrolysis and acid-catalysed methanolysis, to functionalised methyl esters 2 . In the case of chlorotrimethylsilane, hydroxyethyl esters 2′ are isolated. The reaction is also applied to bicyclic orthoesters 3 : whereas β-chloro derivatives and carbonyl compounds gives directly γ-lactones 4 after hydrolysis, the corresponding γ-chloro derivative affords the expected methyl esters after methanolysis.