Palladium-catalysed enantiodivergent synthesis of cis- and trans-4-aminocyclohex-2-enols
作者:Roberto G. P. Gatti、Anna L. E. Larsson、Jan-E. Bäckvall
DOI:10.1039/a600779a
日期:——
Enantiomerically pure cis- and
trans-4-aminocyclohex-2-enols are prepared from
cyclohexa-1,3-diene via
(-)-cis-(1R,4S
)-4-acetoxycyclohex-2-enol (-)-2a using palladium(0)
chemistry. Benzylamine and diethylamine are tested in the
Pd0-catalysed allylic amination reactions. Since acetate is
too slow as a leaving group and gave considerable amounts of side
products, a number of leaving groups have been investigated. Of these
phosphinate and 2,4-dichlorobenzoate are excellent leaving groups and
result in efficient and highly stereoselective reactions; chloride as
allylic leaving group also gives good results. By variation of the
leaving group and proper choice of the protecting group it is possible
to synthesise all four stereoisomers of 4-aminocyclohex-2-enol in good
yield and high enantiomeric excess.
Synthesis of chiral and achiral analogues of ambroxol via palladium-catalysed reactions
作者:Anna L. E. Larsson、Roberto G. P. Gatti、Jan-E. Bäckvall
DOI:10.1039/a702141k
日期:——
Chiral cis- and trans-4-aminocyclohex-2-enols and achiral 4-aminocyclohexanols, which all are analogues of ambroxol, are prepared via stereoselective allylic substitution of cyclohex-2-ene-1,4-diol derivatives or 1-acetoxy-4-chlorocyclohex-2-ene. The chiral target molecules are obtained in enantiomerically pure form by employing a previously described enantiodivergent synthesis of cis- and trans-4-aminocyclohex-2-enols. It has been found that bis(amine) nucleophiles 7a and 7b react only at the benzylic amino group under the conditions employed.