900-91-4Relevant articles and documents
Molecular and supramolecular helicity induction in trityl group-containing compounds: The case of chiral 3,3,3-triphenylpropionic acid derivatives
Skowronek, Pawe?,Czapik, Agnieszka,Rajska, Zuzanna,Kwit, Marcin
, p. 4497 - 4505 (2019/07/08)
The process of dynamic chirality transmission from permanent chirality element to stereodynamic triphenylmethyl group placed in the distance of 4 bonds, has been studied for series of optically active 3,3,3-triphenylpropionic acid derivatives. Structural
Carbon-Skeletal Anionic Rearrangements and the ?-Orbital Overlap Constraint: The Question of Nucleophilic Attack versus Electron Transfer
Eisch, John J.,Kovacs, Csaba A.,Chobe, Prabohd
, p. 1275 - 1284 (2007/10/02)
In order to evaluate the geometrical requirements and the actual electronic nature of apparent anionic rearrangements of metalated aromatic hydrocarbons, amines, and ethers, cyclic structural types of such anions were generated as lithium salts by proton abstraction from C-H bonds by RLi or by C-Cl bond cleavage by Li.The cyclic systems examined were anions of 9,9-dimethyl-, 9-methyl-9-benzyl-, and 9-benzyl-9-phenylfluorenes; 9-methyl-9-phenyl-, 9,9-diphenyl-, and 9,9-(2,2'-biphenylene)-9,10-dihydrophenanthrenes; 5-methyl- and 5-phenyl-5,6-dihydrophenathridines;and 9H-dibenzopyran.The anions generated from 9-methyl-9-benzylfluorene, 9-benzyl-9-phenylfluorene, 5-methyl-5,6-dihydrophenanthridine, and 9H-dibenzopyran, as well as 9-methyl-9-(lithiomethyl)fluorene, did not undergo skeletal rearrangement when heated between 40 and 120 deg C for protracted periods.However, the anions derived from the 9-methyl-9-phenyl-, 9,9-diphenyl-, and 9,9-(2,2'-biphenylene)-9,10-dihydrophenanthrenes did undergo rearrangement with a shift of the 9-aryl group.With the anion of 5-phenyl-5,6-dihydrophenanthridine, some shift of the 5-phenyl was observed, but the principal rearrangement was ring contraction with the formation of N-phenyl-9-fluorenylamine.By noting which anions underwent skeletal rearrangement and which competing migrating groups in a given anion underwent a shift preferentially, we have formulated an appropriate geometrical view of the transition states involved.Furthermore, by generating the 2,2,2-triphenylethyl anion (as its lithium salt) from (a) 2-chloro-1,1,1-triphenylethane and Li, (b) 2-bromo-1,1,1-triphenylethane and n-BuLi, and (c) bis(2,2,2-triphenylethyl)mercury and n-BuLi, we attempted to learn whether such shifts were truly nucleophilic or whether SET processes were involved.Evidence for SET processes was obtained for the generation of (2,2,2-triphenylethyl)lithium by method a, but no ESR or CIDNP evidence for radical intermediates was observable when (2,2,2-triphenylethyl)lithium was produced by method c.
