TY  - JOUR
A1  - Krüger, Tobias
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Linker, Torsten
T1  - Simple Synthesis of gamma-Spirolactams by Birch Reduction of Benzoic Acids
JF  - European journal of organic chemistry
N2  - A convenient synthesis of gamma-spirolactams in only two steps was developed. Birch reduction of benzoic acids and immediate alkylation with chloroacetonitrile afforded cyclohexadienes in high yields. The products could be isolated by crystallization on a large scale in analytically pure form. Subsequent hydrogenation with platinum(IV) oxide as the catalyst reduced the nitrile functionality and the double bonds in the same step with excellent stereoselectivity. The relative configurations were determined unequivocally by X-ray analyses. Direct cyclization of the intermediary formed amino acids afforded the desired gamma-spirolactams in excellent overall yields. The procedure is characterized by few steps, cheap reagents, and can be performed on a large scale, interesting for industrial processes.
KW  - Diastereoselectivity
KW  - Hydrogenation
KW  - Lactams
KW  - Reduction
KW  - Synthetic methods
Y1  - 2016
U6  - https://doi.org/10.1002/ejoc.201601650
SN  - 1434-193X
SN  - 1099-0690
IS  - 6
SP  - 1074
EP  - 1077
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Dzambaski, Zdravko
A1  - Markovic, Rade
A1  - Kleinpeter, Erich
A1  - Baranac-Stojanovic, Marija
T1  - 2-Alkylidene-4-oxothiazolidine S-oxides - synthesis and stereochemistry
JF  - Tetrahedron
N2  - A series of 5-unsubstituted and 5-substituted 2-alkylidene-4-oxothiazolidine-S-oxides were synthesized by the sulfur-oxidation with m-CPBA. The stereochemistry of 5-substituted sulfoxides was determined by means of NMR spectroscopy and DFT theoretical calculations. It was found that the thermodynamically less stable anti-isomer was initially formed in the course of the oxidation, but it underwent epimerization to the mixture enriched in the more stable syn-isomer, during the work-up process. The higher stability of syn-isomers is ascribed to the stronger hyperconjugative sigma(C-H)->sigma*(S-O) interaction versus the weaker sigma(C-C)->sigma*(S-O) delocalization in their anti-counterparts and to the existence of intramolecular 1,5-CH center dot center dot center dot C hydrogen bonds.
KW  - 2-Alkylidene-4-oxothiazolidine
KW  - Sulfoxide
KW  - Diastereoselectivity
KW  - Density functional calculations
KW  - CH center dot center dot center dot O hydrogen bonds
Y1  - 2013
U6  - https://doi.org/10.1016/j.tet.2013.05.087
SN  - 0040-4020
VL  - 69
IS  - 31
SP  - 6436
EP  - 6447
PB  - Elsevier
CY  - Oxford
ER  -