Showing papers by "Matthias Breuning published in 2010"
TL;DR: The zinc dichlorido and zinc diacetato complexes of the chiral tricyclic 9-oxabispidine (1R,2S,9S)-11-methyl-13-oxa-7,11-diazatricyclo [7.3.1.02,7] tridecane were prepared and characterized by X-ray crystallography as mentioned in this paper.
20 citations
TL;DR: In this paper, a flexible approach, applica- ble on a gram scale, to chiral 2-endo- substituted 9-oxabispidines was developed, and the key intermediate, a cis-con- figured 6-aminomethylmorpholine-2- carbonitrile, was prepared from (R)-3- aminopropane-1,2-diol and 2-chloro-A.
Abstract: A flexible approach, applica- ble on a gram scale, to chiral 2-endo- substituted 9-oxabispidines was devel- oped. The key intermediate, a cis-con- figured 6-aminomethylmorpholine-2- carbonitrile, was prepared from (R)-3- aminopropane-1,2-diol and 2-chloro- A The 2-endo substituent was introduced by Grignard addition, cyclization, and exo-selective reduction, thus furnishing the enantiomerically pure bi- and tricyclic 9-oxabispidines in 19-59 % yield. The CuCl2 complex of the tricyclic 9-oxabispidine, which car- ries an 2-endo,N-anellated piperidine ring, is an excellent catalyst for enan- tioselective Henry reactions giving the S-configured b-nitro alcohols in 91- 98 % ee (13 examples). Surprisingly, the analogous copper complexes of the bi- cyclic 9-oxabispidines delivered the enantiocomplementary R-configured products in 33-57 % ee. The respective transition states were discussed.