- Synthesis of pyrrolizin-3-ones by flash vacuum pyrolysis of pyrrol-2-ylmethylidene Meldrum's acid derivatives and 3-(pyrrol-2-yl)propenoic esters
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Monosubstituted pyrrolizin-3-ones 1 with substituants at the 1-, 5-, 6- or 7-positions are prepared in excellent yield by flash vacuum pyrolysis (FVP) of appropriate Meldrum's 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.
- Campbell, Shirley E.,Comer, Murray C.,Derbyshire, Paul A.,Despinoy, Xavier L. M.,McNab, Hamish,Morrison, Roderick,Sommerville, Craig C.,Thornley, Craig
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p. 2195 - 2202
(2007/10/03)
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- New Chemistry of Pyrrolizin-3-one: a Concise Route to 3,8-Didehydroheliotridin-5-one
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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.
- McNab, Hamish,Thornley, Craig
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p. 1570 - 1571
(2007/10/02)
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