110743-96-9Relevant articles and documents
Chiral Inductive Diastereoconvergent Friedel–Crafts Alkylation Reaction of Diastereomixtures of Diarylmethanols with 2-Naphthol Derivatives Catalyzed by SnBr4
Suzuki, Nobuharu,Nakata, Kenya
, p. 7075 - 7086 (2017)
A highly diastereoconvergent Friedel–Crafts alkylation reaction of 2-naphthol derivatives with diastereomixtures of diarymethanols bearing a designed chiral auxiliary was achieved by using tin(IV) bromide as a catalyst in nitromethane under mild reaction conditions. The effects of various substituents located on the chiral auxiliary were evaluated, and chiral induction was found to take place via a carbocation through the chelation effect of an oxygen atom in a stereoconvergent manner. The chiral auxiliary was easily deprotected under conventional hydrogenation conditions without affecting the chirality of the starting material. A variety of substrates were transformed successfully, with high yields and selectivities (diastereomeric ratios ≥ 20:1) obtained irrespective of the substitution pattern and the electronic nature of the substrate aromatic rings.
Preparation of chiral α-oxy-[2H1]methyllithiums of 99% ee and determination of their configurational stability
Kapeller, Dagmar,Barth, Roland,Mereiter, Kurt,Hammerschmidt, Friedrich
, p. 914 - 923 (2007/10/03)
(Tributylstannyl)methyl 2,2,6,6-tetramethylpiperidine-1-carboxylate was metalated with t-BuLi/TMEDA at -78 °C and borylated with the mixed borate derived from (R,R)-1,2-dicyclohexylethane-1,2-diol and t-butanol to give diastereomeric boronates 31/32 in equal amounts. Boronates 31 and 32 were reduced with LiBEt3D and then oxidized with basic H2O 2 to give (S)- and (R)-tributylstannyl-[1-2H 2]methanol of 99% ee, respectively. Treatment of their respective phosphates with n-BuLi at -78 and 0 °C gave microscopically configurationally stable phosphinyloxy-substituted [2H 1]methyllithiums, which rearranged to hydroxy-[1-2H 1]-methylphosphonates of ee > 98% (phosphate-phosphonate rearrangement). The N,N-iisopropylcarbamates of the enantiomeric tributylstannyl-[1-2H1]methanols were transmetalated to give carbamoyloxy-substituted chiral [2H1]methyllithiums, which were macroscopically configurationally stable for prolonged periods of time (up to 3 h, ee still 99%) at -78 °C, deduced from trapping experiments with benzaldehyde. The chemical stability of these methyllithiums ended at -50 °C. The stereochemistry of the monoprotected and monodeuterated 1-phenylethane-1,2-diols obtained was secured by spectroscopic comparison of their Mosher esters with that of all four stereoisomeric 1-phenyl-[1- 2H1]ethane-1,2-diols synthesized independently. Furthermore, the configurations of the boronates and the chiral methyllithiums derived from them were deduced from a single-crystal X-ray structure analysis of a carbamate in which the tributylstannyl group had been replaced by the [(1R)-menthyl]dimethylstannyl group.
