David Guijarro

Naphthalene-catalysed lithiation of allylic and benzylic mesylates: a new method for allyl, methallyl, and benzyl lithium

Abstract The reaction of allylic or benzylic mesylates ( 1 with an excess of lithium powder and a catalytic amount of naphthalene (4 mol %) in THF at −78°C leads to a solution of the corresponding organolithium derivatives, which by treatment with different electrophiles yield the expected products 2–7 . As an alternative route, the process can be carried out at 0°C by adding the corresponding mesylate together with the electrophile to a suspension of the activated lithium in THF, in a Barbier-type reaction.

Naphthalene-catalysed lithiation of phenone imines in the presence of carbonyl compounds : preparation of 1,2-aminoalcohols

Abstract The lithiation of different phenone imines 1 with an excess of lithium powder and a catalytic amount (8 mol %) of naphthalene in the presence of several carbonyl compounds 2 in tetrahydrofuran at temperatures ranging between −78 and 20°C leads, after hydrolysis with water, to the corresponding 1,2-aminoalcohols 3 in moderate yields.

Naphthalene-catalysed lithiation of dialkyl sulfates : a new route for organolithium reagents

Abstract The lithiation of primary and secondary dialkyl sulfates with an excess of lithium powder in the presence of a catalytic amount of naphthalene at −78°C leads to the corresponding alkyl-lithium reagents (1:2 molar ratio), which react with different electrophiles, mainly carbonyl compounds, to yield the expected coupling products. This methodology represents an indirect way for transforming alcohols into organolithium compounds through the corresponding dialkyl sulfates.

Organolithium reagents by reductive decyanation of nitriles with lithium and a catalytic amount of 4,4-'Di-tert-butyl-biphenyl in a Barbier-type reaction

Abstract The reaction of different nitriles 1 with an excess of lithium powder (1:14 molar ratio) and a catalytic amount of 4,4′-di-tert-butylbiphenyl (5 mol %) in the presence of a carbonyl compound (Barbier-type conditions) in THF at low temperature (−30 or −78°C) leads to the corresponding compounds 2 resulting from the coupling between the electrophile and the organolithium intermediate arising from a reductive decyanation of the starting nitrile 1. This new reaction can be also applied to the use of trimethylchlorosilane as electrophile at 0°C.

A Versatile Ru Catalyst for the Asymmetric Transfer Hydrogenation of Both Aromatic and Aliphatic Sulfinylimines

A highly efficient Ru catalyst based on an achiral, very simple, and inexpensive amino alcohol ligand (2-amino-2-methylpropan-1-ol) has been developed for the asymmetric transfer hydrogenation (ATH) of chiral N-(tert-butylsulfinyl)imines. This complex is able to catalyze the ATH of both aromatic and the most challenging aliphatic sulfinylimines by using isopropyl alcohol as the hydrogen source. The diastereoselective reduction of aromatic, heteroaromatic, and aliphatic sulfinylketimines, including sterically congested cases, over short reaction times (1-4u2005h), followed by desulfinylation of the nitrogen atom, affords the corresponding highly enantiomerically enriched (ee up to >99u2009%) α-branched primary amines in excellent yields. The same ligand was equally effective for the synthesis of both (R)- and (S)-amines by using the appropriate absolute configuration in the iminic substrate. DFT mechanistic studies show that the hydrogen-transfer process is stepwise. Moreover, the origin of the diastereoselectivity has been rationalized.

C,O-Dilithiated Diarylmethanols: Easy and Improved Preparation by Naphthalene-Catalysed Lithiation of Diaryl Ketones and Reactivity Toward Electrophiles

Abstract The lithiation of different diaryl ketones 1 with an excess of lithium powder and a catalytic amount (8 mol %) of naphthalene in tetrahydrofuran at −30°C leads to the formation of the corresponding dianions of the type I, with Met=Li, which react with several electrophiles (E+=MeI, EtBr, PriCHO, PhCHO, cyclohexanone, MeCN) to give, after hydrolysis, the expected substituted diarylmethanols 2.

Direct transformation of trialkyl phosphates into organolithium compounds by a DTBB-catalysed lithiation

Abstract The reaction of different alkylic or phenylic phosphates 1 with an excess of lithium powder and a catalytic amount of DTBB (5 mol %) in the presenc

DTBB-Catalysed dilithiation of styrene and its methyl-derivatives: introduction of two electrophilic reagents

Abstract The reaction of styrene and some methyl-substituted styrenes 1 with lithium and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB) in the presence of several electrophiles [Me3SiCl, Me2CO, Et2CO, (CH2)5CO, Pr2CO], in THF, at temperatures ranging from −78 to 0°C, gave, after hydrolysis, products 2 resulting from addition of lithium to the olefinic double bond and successive trapping with the electrophilic reagent. When a carbonyl compound was used as electrophile, mixtures of the monoaddition–reduction compounds 3 and 4 were obtained as by-products, which could be easily separated from the diaddition products 2.

Direct transformation of dialkyl sulfates into alkyllithium reagents by a naphthalene-catalysed lithiation

Abstract The lithiation of primary and secondary dialkyl sulfates with an excess of lithium powder in the presence of a catalytic amount of naphthalene (4 mol %) in THF at −78°C leads to the corresponding alkyllithium reagents (1:2 molar ratio) which react with different electrophiles, mainly carbonyl compounds, to yield after hydrolysis, the expected coupling products. This methodology represents an indirect way to transform alcohols into organolithium compounds through the corresponding dialkyl sulfates. When the same procedure is applied to five or six member cyclic sulfates (derived from 1,2- or 1,3-diols) only products arising from a β- or γ-elimination process (giving olefins or cyclopropanes), respectively, are obtained.

Naphthalene-catalysed reductive desulfonylation with lithium : alkyllithiums from alkyl phenyl sulfones

Abstract The reaction of alkyl aryl sulfones 1 with an excess of lithium powder and a catalytic amount of naphthalene (8 mol %) in the presence of a carbonyl compound [PriCHO, PhCHO, Et2CO, ( CH 2)5CO] or trimethylchlorosilane (Barbier-type conditions) in THF at temperatures ranging between −78 and 20°C leads, after hydrolysis with water, to the expected coupling products, arising from the corresponding alkyllithium in situ generated, in 30–61% yields.