50710-51-5Relevant 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)
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.
Electrophilic Aromatic Substitution. Part 34. Partial Rate Factors for Detritiation of Dithienobenzene, Dithienobenzene, and Dithienobenzene
Archer, William J.,Cook, Robert,Taylor, Roger
, p. 813 - 820 (2007/10/02)
Dithienobenzene (I), dithienobenzene (II), and dithienobenzene (III), specifically labelled with tritium in each position, have been synthesized.Their rates of protio-detritiation, in either anhydrous trifluoroacetic acid or mixtures of acetic acid and trifluoroacetic acid, have been measured at 70 deg C.The rate-acidity profiles for each compound show that there is weak hydrogen bonding between sulphur and trifluoroacetic acid, and the extent of this is closely similar to that previously found for thienothiophens thereby confirming the general trend observed with sulphur-containing heterocycles viz. that the extent of hydrogen bonding is proportional to the number of sulphur atoms in the aromatic compounds.Partial rate factors for detritiation, free from the effects of hydrogen bonding, are calculated as follows (position and compound in parentheses): 3.42E6 (1)-(I), 1.65E7 (2)-(I), 5.35E5 (4)-(I), 1.525E7 (2)-(II), 4.98E6 (3)-(II), 1.32E6 (4)-(II), 4.59E5 (5)-(II), 2.35E7 (7)-(II), 4.01E6 (8)-(II), 1.96E7 (2)-(III), 3.77E6 (3)-(III), 3.99E5 (4)-(III); the corresponding ?+ values are -0.745, -0.825, -0.655, -0.82, -0.765, -0.70, -0.645, -0.84, -0.755, -0.835, -0.75, and -0.64.The positional reactivity orders both within a given molecule and between molecules are satisfactorily predicted by localization energies calculated by the simple Hueckel method using the parameters αS 1.0, βCS 0.6, these having been found previously to predict correctly the positional reactivities in other sulphur-containing heterocycles.
