Our research group has been studying for several years the reactivity of α,β-unsaturated acetals, as masked acyl anions, in the presence of Li-K mixed bases also called Schlosser-Lochmann mixed bases, easily prepared by mixing 1 or 2 eq. of Na or K alkoxyde with a solution of RLi.1 α,β-Unsaturated acetals afford in a regio- and stereoselective manner functionalised alcoxy-1,3-dienes. The reaction has been extended to cyclic α,β-unsaturated acetals, and several electrophiles have been used.2 In this communication we wish to present our preliminary results on the reactivity of N,α-diarylnitrones with alcoxydienes in the presence of Schlosser-Lochmann superbases. Nitrones, are very interesting substrates, not only known in organic chemistry, but also in medicinal chemistry and polymer science. They show electrophilic character and give nucleophilic addition with several nucleophiles and organometallic reagents.3 Preliminary results obtained using α,N-diarylnitrones as electrophilic partners of metalated alcoxydienes in superbasic medium, seems to indicate the formation of a highly conjugate imine (3) by a domino process. As evidenced in Scheme 1, the addition of the nitrone 2 to the intermediate vinylic carbanion would be followed by the elimination of a hydroxyl species with the formation of an imine by a E1cb. At our knowledge this type of reactivity of α,N-diarylnitrones, partially due to the presence of the LICKOR base, has never been reported. (Scheme 1) The obtained imines were hydrolysed in acidic conditions affording cyclopentenones in good yields. We hypothesised a process where a proton attacks the imine double bond followed by an intramolecular electrophilic addition to the terminal double bond of the dienic portion, finally the elimination of ethanol leads to the corresponding 2-phenylamino-α,β-cyclopentenone

LIC-KOR Promoted Nitrone Reactivity with Metalated Alcoxydienes

PARISOTTO, STEFANO;PRANDI, Cristina;VENTURELLO, Paolo
2015-01-01

Abstract

Our research group has been studying for several years the reactivity of α,β-unsaturated acetals, as masked acyl anions, in the presence of Li-K mixed bases also called Schlosser-Lochmann mixed bases, easily prepared by mixing 1 or 2 eq. of Na or K alkoxyde with a solution of RLi.1 α,β-Unsaturated acetals afford in a regio- and stereoselective manner functionalised alcoxy-1,3-dienes. The reaction has been extended to cyclic α,β-unsaturated acetals, and several electrophiles have been used.2 In this communication we wish to present our preliminary results on the reactivity of N,α-diarylnitrones with alcoxydienes in the presence of Schlosser-Lochmann superbases. Nitrones, are very interesting substrates, not only known in organic chemistry, but also in medicinal chemistry and polymer science. They show electrophilic character and give nucleophilic addition with several nucleophiles and organometallic reagents.3 Preliminary results obtained using α,N-diarylnitrones as electrophilic partners of metalated alcoxydienes in superbasic medium, seems to indicate the formation of a highly conjugate imine (3) by a domino process. As evidenced in Scheme 1, the addition of the nitrone 2 to the intermediate vinylic carbanion would be followed by the elimination of a hydroxyl species with the formation of an imine by a E1cb. At our knowledge this type of reactivity of α,N-diarylnitrones, partially due to the presence of the LICKOR base, has never been reported. (Scheme 1) The obtained imines were hydrolysed in acidic conditions affording cyclopentenones in good yields. We hypothesised a process where a proton attacks the imine double bond followed by an intramolecular electrophilic addition to the terminal double bond of the dienic portion, finally the elimination of ethanol leads to the corresponding 2-phenylamino-α,β-cyclopentenone
OMCOS18 - Organometallic Chemistry Directed Towards Organic Synthesis
Sitges (Barcellona)
28/06 - 02/07 2015
OMCOS18 Abstract book
OMCOS18 IUPAC
P-273
P-273
LICKOR, NTRONES, ALCOXYDIENES
Dr Annamaria Deagostino, Stefano Parisotto, prof Cristina Prandi, prof Paolo Venturello
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1576223
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