4594-82-5Relevant articles and documents
Enantioselective Hydroazidation of Trisubstituted Non-Activated Alkenes
Meyer, Daniel,Renaud, Philippe
, p. 10858 - 10861 (2017/08/30)
A one-pot procedure for the enantioselective hydroazidation of non-activated trisubstituted alkenes is described. Hydroboration with monoisopinocampheylborane (IpcBH2) provides dialkylboranes that are in situ selectively converted into monoalkyl-substituted catecholboranes; these undergo radical azidation upon treatment with benzenesulfonyl azide and a radical initiator. Enantiomerically enriched azides were thus obtained in yields of 59–81 % and enantioselectivities of up to 94:6 e.r. (98:2 e.r. if the intermediate dialkylborane is purified by crystallization). A rapid access to enantiomerically pure (+)-rodocaine is also described. The use of other arenesulfonyl radical traps enables enantioselective hydroallylation, hydrosulfanylation, and hydrobromination reactions with yields of 71–86 %.
Diastereoselective access to trans -2-substituted cyclopentylamines
Joosten, Antoine,Lambert, Emilie,Vasse, Jean-Luc,Szymoniak, Jan
supporting information; experimental part, p. 5128 - 5131 (2011/01/05)
A highly diastereoselective synthesis of trans-2-substituted cyclopentylamines via a tandem hydrozirconation/Lewis acid-mediated cyclization sequence applied to butenyl oxazolidines is described. The method allows an easy preparation of diversely substituted cyclopentylamines which appear to be useful synthetic intermediates. This was further illustrated by the syntheses of (±)-Rodocaine, (±)-trans-pentacin, and enantiomerically enriched trans-cyclopentane-1,2-diamine.
ENAMINE CHEMISTRY-XXIV. SYNTHESIS, THIATION, AND REDUCTION OF LACTAMS
El-Barbary, A. A.,Carlsson, S.,Lawesson, S.-O.
, p. 405 - 412 (2007/10/02)
Enamines, 1, prepared from cyclohexanones or cyclopentanones are reacted with acrylamide to give lactams, the condensed 2-piperidones, 2.Ethyl 2-(1-pyrrolidinyl)-2-cyclohexene-1-propanoate, 3, when treated with primary amines, produces the corresponding N-substituted 2-piperidones, 4.Ethyl 2-(1-pyrrolidinyl)-2-cyclohexene-1-ethanoates and ethyl 2-(1-pyrrolidinyl)-2-cyclopentene-1-ethanoate, 5, react with primary amines to give condensed N-substituted 2-pyrrolidones, 6, and non-cyclic imines, 7.The starting enamines , 1, treated with 2-bromo acetamides only afford the N-alkylated compounds, 8 (2-pyrrolidino acetamides), and the regioselectivity of this reaction is rationalized in terms of the HSAB-principle.Compound 1 undergoes an exchange reaction (aminolysis) when reacted with primary amines to give the imines 9.Thiation of the lactams 2 and 6 with the Lawesson reagent (LR), affords the corresponding thiolactams, 10.Reduction of the lactams and thiolactams, 2, 6, and 10 by LAH gives the imines, 11, and the enamines, 16.Further reduction of 11 (LAH) affords the saturated amines, 15.The stereochemistry for the formation of 15 is discussed using the torsion angle notation and the principal of least torsional distortion.In a one-pot reaction using LAH-acetic anhydride the lactams, 2, and the thiolactams, 10, are transformed into the enamides, 14.Compound 14 was also obtained from 11 by direct acetylation with acetic anhydride in the presence of triethylamine.
