作者:Hamish McNab、James Montgomery、Simon Parsons、David G. Tredgett
DOI:10.1039/c0ob00116c
日期:——
Pyrrolizine-1,3-dione 4 was made by oxidation of the alcohol 2 using pyridinium chlorochromate. The dione 4 shows ketone properties (e.g. formation of DNP derivative 11) and, in common with other pyrrolizinones, the lactam unit is readily ring-opened by methanol under basic conditions. The active methylene unit of 4 couples readily with diazonium salts to provide the hydrazone 15 whose structure was confirmed by X-ray crystallography. The ‘Meldrumsated’ derivative 18 exists exclusively as the tautomer 18F; flash vacuum pyrolysis (FVP) of 18 at 700 °C gives the pyronopyrrolizine 20 exclusively. Reaction of 4 with DMF acetal gives the dimethylaminomethylene derivative 22 which exists as a mixture of rotamers at room temperature.
New chemistry of pyrrolizin-3-one: a concise route to 3,8-didehydroheliotridin-5-one
作者:Hamish McNab、Craig Thornley
DOI:10.1039/c39930001570
日期:——
1-Substituted 1,2-dihydropyrrolizin-3-ones can be obtained from pyrrolizin-3-one 2 by conjugate nucleophilic addition or electrophilic addition reactions; the 1-chloro compound 9 obtained by the latter method is used as a key intermediate in a six-step synthesis of the title compound 3 from 4-acetoxymethylpyridine-N-oxide.
Chemistry of pyrrolizinones. Part 1. Reactions of pyrrolizin-3-ones with electrophiles: synthesis of 3,8-didehydroheliotridin-5-one 1
作者:Hamish McNab、(the late) Craig Thornley
DOI:10.1039/b005620k
日期:——
The reaction of pyrrolizin-3-one 1 with dry hydrogen chloride gives the 1-chloro-1,2-dihydro derivative 8 (93%) by electrophilic addition. The halogen of 8 is readily displaced by O-nucleophiles to give 6, 9 or 10 in 87–100% yield, and this strategy has been employed in a short synthesis of the necine base didehydroheliotridin-5-one 4. Pyrrolizinone 1 can be brominated by N-bromosuccinimide in the