Arene-Catalyzed Lithiation Research Articles

Arene-catalysed lithiation of triflates and triflamides under barbier-type conditions: An indirect transformation of alcohols and amines into organolithium compounds

The reaction of alkyl triflates 1 or allyl or benzyl triflamides 3 with an excess of lithium powder and a catalytic amount of naphthalene (4 mol %) in the presence of different electrophiles [Me 3SiCl, Pr iCHO, Bu tCHO, PhCHO, 4-MeOC 6H 4CHO, CH 3(CH 2) 6CHO, Et 2CO, (CH 2) 5CO, ( c-C 3H 5) 2CO, PhCOMe, 4-MeC 6H 4COPh, PhCH=NPh, n-C 8H 7CON(CH 2) 4] in THF at temperature ranging between −78 and 0°C leads, after hydrolysis with water, to the corresponding condensation products 2. When α,β-unsaturated carbonyl compounds are used as electrophilic compounds 1,2- (2-cyclohexenone) or 1,4-addition (cinnamaldehyde or benzylideneacetone) takes places depending on the electrophile used.

Arene-catalysed lithiation reactions

Arene-catalysed lithiation reactions

Reductive Cleavage of Allyllic Ketals by an Arene-Catalysed Lithiation: A Simple and Direct Route to Masked Lithium Homoenolates

The reaction of acrolein diethyl acetal 1 with an excess of lithium powder and a catalytic amount of 4,4′-di- tert-butylbiphenyl (DTBB; 2.5 mol %) in the presence of a carbonyl compound 2 in THF at 0°C leads, after hydrolysis with water, to the corresponding γ-coupling products 3 as a Z/E mixture, the Z-isomer being mainly the major one. When the final hydrolysis was carried out in acidic conditions (3 N hydrochloric acid) followed by treatment with silicon compounds of the type R 3SiNu in the presence of boron trifluoride etherate in dichloromethane at temperatures ranging between −78 and 20°C, the corresponding substituted tetrahydrofurans 4 were obtained. The same Barbier-type reaction applied to 2-cyclopentenone ethylene ketal 5 yields, after acid hydrolysis, the expected 3-substituted cyclopentanones 6. In all cases overall yields are moderates.

Arene-catalysed lithiation of 1,4-dichlorobut-2-enes and 3,4-dichlorobut-1-ene and reaction with electrophiles: A common reaction pathway

The reaction of ( Z) or ( E)-1,4-dichlorobut-2-ene ( 1, 2), or 3,4-diclorobut-1-ene ( 3) with an excess of lithium powder and a catalytic amount of 4,4′-di- tert-butylbiphenyl (5 mol %) in the presence of an electrophile [(CH 2) 4CO, Bu tCHO, Me 3SiCl] in THF at O°C yields, after hydrolysis, the corresponding 1,4- and 1,2-disubstituted compounds ( Z/E)- 4 and 5, the ratio of them being independent on the starting material. In the case of compounds 4 the Z-diastereomer is largely the major one. When dichlorodiethylsilane was used as electrophile the corresponding substituted silacyclopentene 6 was the only reaction product isolated. A possible mechanism involving dilithiated species is proposed.

Dichloromethane as a source of the CH 22-synthon: A combination of an arene-catalysed lithiation and a barbier-type reaction

The reaction of dichloromethane 1 with an excess of lithium powder (1:7 molar ratio) and a catalytic amount of 4,4′-di- tert-butylbiphenyl (5 mol %) in the presence of a carbonyl compound 2 (1:2 molar ratio) in tetrahydrofuran at −40°C yields, after hydrolysis, the corresponding 1,3-diols 3 in moderate yields. The process can be also applied to more complicated gem-dichloro derivatives such as 7,7-dichlorobicyclo[4.1.0]heptane 6 or methyl dichloromethyl ether 9.

Arene-catalysed lithiation reactions with lithium at low temperature

The reaction of functionalized alkyl chlorides or phenyl sulphides with an excess of lithium powder in the presence of a catalytic amount of an arene (1%; naphthalene, biphenyl, 4,4′-di-tert-butylbiphenyl) in tetrahydrofuran (THF) at –78 °C gives the corresponding organolithium compounds, which react with electrophiles such as water, iso-butyraldehyde, or cyclohexanone to yield the expected reaction products.