173907-96-5Relevant academic research and scientific papers
Formation of carbocycles by intramolecular conjugate displacement: Scopeand mechanistic insights
Wang, Lihong,Prabhudas, Bodhuri,Clive, Derrick L. J.
supporting information; experimental part, p. 6003 - 6012 (2009/09/25)
A detailed study has been made of a method of ring closure categorized as an all-carbon intramolecular conjugate displacement (ICD). This reaction involves intramolecular addition of a carbanion, which is stabilized by at least one electron-withdrawing group, to a Michael acceptor which has a leaving group in an allylic position. The process formally resembles a combination of Michael addition and S N2' displacement. The overall result is formation of a ring with loss of the allylic leaving group and shift of the original double bond to a new location spanning the positions of the electron-withdrawing substituent of the Michael acceptor subunit and the original allylic leaving group. The starting materials are easily prepared by a selenium-based version of the Morita-Baylis-Hillman reaction. The cyclizations are transition metal free and occur under mild conditions, using DBU or Cs 2CO 3 inMeCN or THF. Acetate is a suitable leaving group and the electron-withd rawing substituent of the Michael acceptor unit can be CO 2R,SO 2Ph, or CN. Six- and seven-membered rings are formed effi ciently, and complex structures, such as those resembling the core of CP-225,917, are easily assembled. The products of these ICD reactions are themselves classical Michael acceptors. A range of mechanisms probably operates, depending on the structure of the starting material and the reaction conditions, but conclusive evidence for a stepwise mechanism was obtained in a suitably biased case, while other observations are compatible with a concerted process or a stepwise path involving a short-lived carbanion that evades capture by a proton source.
Stereodivergent diversity oriented synthesis of piperidine alkaloids
Adriaenssens, Louis V.,Austin, Carolyn A.,Gibson, Mairi,Smith, David,Hartley, Richard C.
, p. 4998 - 5001 (2007/10/03)
Alkylidenetitanium reagents enable the reagent-controlled high throughput asymmetric synthesis of 2-substituted piperidines and rapid access to multiple cyclic imines using solid phase synthesis (SPS). The Schrock carbenes, generated by reduction of thioacetals, convert resin-bound esters into enol ethers. Treatment with acid releases amino ketones that are cyclized with TMSCl to give iminium salts. Reduction introduces a chiral centre at C-2, whose absolute stereochemistry is determined by a phenethylamine (PEA) chiral auxiliary. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
Yield and selectivity enhancement by trimethylsilyl chloride in the conjugate addition of stabilized organolithiums
Hong, Liu,Cohen, Theodore
, p. 8925 - 8928 (2007/10/02)
The yield and selectivity in the conjugate addition of some stabilized organolithiums to α,β-unsaturated carbonyl compounds, especially easily polymerized ones, are increased in the presence of trimethylsilyl chloride, alone or in combination with hexamethylphosphoric triamide. E-silyl enol ethers bearing the versatile phenylthio group are obtained prior to hydrolysis. Some synthetic uses are demonstrated.
