Compounds with bridgehead nitrogen: 45—the ¹H NMR spectra and stereochemistry of some dimethylperhydro‐oxazolo[3,4‐a]pyridines

Compounds with bridgehead nitrogen. 57—NMR spectra and stereochemistry of protonated perhydrooxazolo [3,4‐a]pyridines, perhydropyrido[1,2‐c] [1,3] oxazine and perhydropyrido[1,2‐c] [1,3]oxazepine

“…The cisltrans proportions of the perhydropyridoC 1,2-c] [ 1,3]oxazine hydrochlorides are shifted, compared with the free base equilibria, towards the 0-inside cisfused isomer, explained again by the increased lone pair availability in 5b.…”

“…The positions of conformational equilibria in CDCl, solution at 25 "C for perhydrooxazolo[3,4-a]pyridine (1) (67% l a e 33% lb),2-4 perhydropyrid0[1,2-~][1,3]-oxazine (5) (90% 5a e 10% 5b) ' and perhydropyrido[l, 2-c] [1,3]oxazepine (9) (74% 9a T= 26% 9b)6 have been established by 'H and I3C NMR techniques. Protonation of 1, 2 and 3 to give the isomeric trans and cis salts (e.g.…”

A highly rigid ditopic conjugate with orthogonal coordination axes and its zinc(ii) and copper(ii) complexes

“…Compound 2 had previously been made by reacting a Grignard reagent with the nitrile derivative. 25 We developed a new efficient route inspired by the procedure described by Holm et al, 26 which afforded 2 in 52% yield.…”

Synthetic Study toward Total Synthesis of (±)-Germine: Synthesis of (±)-4-Methylenegermine

“…The dienophile 23 was synthesized by a Wadsworth–Emmons condensation between siloxyaldehyde 24 and the phosphonate 25 , accessible by the coupling of 2-cyano-5-methylpyridine with dimethyl methylphosphonate. The Diels–Alder adduct 26 was then obtained, in refluxing toluene with 23 , in the presence of the inhibitor, 3- tert -butyl-4-hydroxy-5-methylphenyl sulfide, in about 88% yield, apparently as a single substance (Scheme ).…”