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.
Synthesis of pyrrolizin-3-ones by flash vacuum pyrolysis of pyrrol-2-ylmethylidene Meldrum’s acid derivatives and 3-(pyrrol-2-yl)propenoic esters
作者:Shirley E. Campbell、Murray C. Comer、Paul A. Derbyshire、Xavier L. M. Despinoy、Hamish McNab、Roderick Morrison、Craig C. Sommerville、Craig Thornley
DOI:10.1039/a701749i
日期:——
Monosubstituted pyrrolizin-3-ones 1 with substituents at the 1-, 5-,
6- or 7-positions are prepared in excellent yield by flash vacuum
pyrolysis (FVP) of appropriate Meldrumâs acid derivatives 2. The
mechanism involves formation of the pyrrol-2-ylmethylideneketene 29,
which can also be generated thermally from 3-(pyrrol-2-yl)propenoate
esters (e.g. 30). This alternative route has been used to make
a range of 2-substituted pyrrolizin-3-ones, again in excellent yield.
The 3-oxo-3H-pyrrolizine-2-carboxylic acid 42 could not be made
in this way owing to facile decarboxylation to pyrrolizinone 1, and
extension to the formation of the azaazulenone 48 was again
unsuccessful.
Hydrogenation of pyrrolizin-3-ones; new routes to pyrrolizidines
作者:Xavier L. M. Despinoy、Hamish McNab
DOI:10.1039/b910199c
日期:——
catalysts. Good diastereoselectivity (up to >97:3, depending on catalysts and solvent) can be achieved if the pyrrolizin-3-one is substituted at the 1- (or 7-) position(s), but the selectivity is reduced if both positions are substituted. Subsequent deoxygenation of the pyrrolizidin-3-ones provides concise, diastereoselectiveroutes to the necine bases (±)-heliotridane 5, (±)-isoretronecanol 6 and (±)retronecanol