Saturated Bicyclic 6/5 Ring Fused Systems with Bridgehead Nitrogen and a Single Additional Heeroatom

Enantiopure bicyclic piperidinones: stereoselectivity in lactam enolate alkylations

“…When the dimethyl derivative (±)-2c was treated with LDA and either p-nitrobenzyl bromide or methyl iodide, derivatives 5a,b and 6a,b were obtained in modest yields of 28% and 43% respectively but with no diastereocontrol. Related bicyclo[4.3.0] heterocycles have been shown to exhibit significant conformational fluxionality, 74 and this may account for the lack of diastereoselectivity observed in the alkylations of 2c: for this compound, the presence of two methyl substituents at C(2) means that no steric advantage is achieved in a conformational equilibrium, unlike 2a, where the C(2)Ph is presumably in a (pseudo)equatorial position. That disubstitution was feasible was evident by the initial introduction of an ester function (NaH, diethyl carbonate) to give 7a in 81% yield followed by selenenylation (NaH, PhSeCl, 70%) leading to 7b, but without diastereocontrol, or by direct double selenenylation (LiHMDS, PhSeCl, 50%) leading to 7c.…”

Synthesis, Molecular Structure, Conformational Analysis, and Chemical Properties of Silicon-Containing Derivatives of Quinolizidine

“…Hundreds of quinolizidine alkaloids of plant origin have been isolated and investigated. , This wide spreading in nature, the biological activity and the unique structure of quinolizidine derivatives stimulated the elaboration of methods for their synthesis as well as the investigation of their conformational behavior, of their reactivity and potential applications (see, e.g., refs − and references cited therein).…”

“…The FT-IR spectra were taken in KBr pellets and CCl 4 or CH 2 Cl 2 solution. The 1 H, 13 C, 15 N and 29 Si NMR spectra were registered for 10−20% solutions on a 400 MHz instrument at 400.1, 100.6, 40.5, and 79.5 MHz, respectively. Chemical shifts are given relative to TMS ( 1 H, 13 C, 29 Si) or MeNO 2 ( 15 N).…”

“…The 1 H, 13 C, 15 N and 29 Si NMR spectra were registered for 10−20% solutions on a 400 MHz instrument at 400.1, 100.6, 40.5, and 79.5 MHz, respectively. Chemical shifts are given relative to TMS ( 1 H, 13 C, 29 Si) or MeNO 2 ( 15 N). 15 N NMR chemical shifts were obtained from HMBC spectra recorded by the use of a gradient probe working in the hmbcgp mode optimized to the longrange coupling constant J NH of 9 Hz.…”

“…The mixture was cooled, excess of hexamethyldisilazane evacuated to obtain viscous oil, which was slowly crystallized. 13 C NMR (CD 3 CN), δ C , ppm: −2.5 (SiMe), −1.6 (SiMe), −0.4(SiMe 3 ), 47.9 (SiCN), 54.7 (CH 2 OH), 61.4 (NCC), 66.1 (OCC). 15 N NMR (CD 3 CN), δ N , ppm: −343.8.…”