32059-75-9Relevant articles and documents
Effect of base on alkyltriphenylphosphonium salts in polar aprotic solvents
Ngwendson, Julius N.,Schultze, Cassandra M.,Bollinger, Jordan W.,Banerjee, Anamitro
, p. 668 - 675 (2008/09/21)
When arylmethyl phosphonium salts are treated with a base (e.g., t-BuOK or NaH) they homocouple to form symmetric 1,2-diarylethenes. In some cases, dilution and (or) use of excess base lead to very high yields of the product. This reaction is solvent sensitive: the reaction occurs only when polar aprotic solvents such as acetonitrile or DMSO are used. Other alkyl phosphonium salts (e.g., ethoxycarbonylmethyltriphenylphosphonium bromide and n- butyltriphenylphosphonium bromide) form a ylid (when an α-carbonyl group is present) or lose a phenyl group to form alkyldiphenylphosphine oxides when treated with the base. Mechanistic investigation of the homocoupling reaction indicates that the reaction proceeds through a ylid that acts as a nucleophile on an unreacted phosphonium salt. The resulting adduct undergoes elimination to form the observed product. The EIZ ratio seems to depend on the amount of the base used and the phosphonium salt involved.
ALKYLATION ORIENTATION RULES IN CONJUGATE ADDITION OF GRIGNARD REAGENTS TO NITROPYRROLE AND NITROTHIOPHENE SYSTEMS
Ballini, Roberto,Bartoli, Giuseppe,Bosco, Marcella,Dalpozzo, Renato,Marcantoni, Enrico
, p. 6435 - 6440 (2007/10/02)
Conjugate addition of various Grignard reagents to 1-alkyl-2-nitropyrroles and to 2-nitrothiophene has been investigated. 1-Alkyl-2-nitropyrroles undergo alkylation at 3 and 5 positions with prevalence of the latter isomer.On the contrary, in the 2-nitrothiophene system, formation of the 3-isomer prevails.In both systems, a bulkier Grignard reagent favours the 5-isomer formation.This trend can be reversed increasing steric hindrance exerted by the 1-substituent of 2-nitropyrrole. 1-(Tri-isopropylsilyl)-3-nitropyrrole and 3-nitrothiophene give exclusively the 2-isomer.This reaction allows 2-alkyl-3-nitrothiophenes and pyrroles to be synthesized with a one-pot procedure instead of the classical multi stage reaction.