289673-85-4Relevant academic research and scientific papers
Solvent and ligand effects associated with the Rh(II)-catalyzed reactions of α-diazo-substituted amido esters
Padwa, Albert,Zou, Yan
, p. 1802 - 1808 (2015)
We report a detailed investigation into the Rh(II)-catalyzed reactions of 2-alkynyl 2-diazo amido-substituted esters. The distribution of products was found to be dependent on the substituent group on the nitrogen atom, the ligand on the Rh(II) center, and the solvent used. The dominant product obtained from the reaction of 3-(trimethylsilyl)prop-2-ynyl-2-(dibenzylcarbamoyl)-2-diazoacetate (34) with Rh2(OAc)4 in hexane corresponds to an azetidinone derived by CH-insertion of the carbenoid into the neighboring benzyl group. In contrast, the Rh2(esp)2-catalyzed reaction of 34 in CH2Cl2 afforded a 3-oxocyclohepta[c]pyrrole formed by cyclopropanation of the rhodium carbenoid across the aromatic π-bond. Related systems were studied, and CH-insertion into an adjacent alkyl group was found to be the dominant or exclusive pathway. In none of the cases studied was it possible to detect products derived from a carbenoid/alkyne cascade sequence as had previously been found with a series of 2-alkynyl-2-diazo-3-oxobutanoates.
Synthesis of furo[3,4-c]furans using a rhodium(II)-catalyzed cyclization/Diels - Alder cycloaddition sequence
Padwa, Albert,Straub, Christopher S.
, p. 227 - 239 (2007/10/03)
A series of 2-alkynyl 2-diazo-3-oxobutanoates, when treated with a catalytic quantity of rhodium(II) acetate, afforded furo[3,4-c]furans in good yield. The reaction proceeds by addition of a rhodium-stablilized carbenoid onto the acetylenic π-bond to give a vinyl carbenoid that subsequently cyclizes onto the neighboring carbonyl group to produce the furan ring. These furo[3,4-c]furans react with various dienophiles, furnishing anisole derivatives derived by loss of water from the initially formed Diels - Alder cycloadducts. The Rh(II)-catalyzed cyclization reaction was quite versatile with regard to the nature of the interacting carbonyl group. The methodology was applied to the synthesis of several oxa-polyheterocyclic systems by first generating a 2-alkoxy-substituted furan and then allowing it to undergo a subsequent intramolecular Diels - Alder cycloaddition. Ring opening of the resulting cycloadduct is followed by deprotonation to furnish a rearranged keto lactone. The potential use of this method for the synthesis of the alkaloid strychnine was probed using suitable model diazo compounds. To establish the viability of this approach, the Rh(II)-catalyzed cyclization/cycloaddition sequence of α-diazo amides 64 and 68 were studied. Both compounds underwent the sequential process in good overall yield, leading to novel pentacyclic products. The structural features of the resultant products present numerous opportunities for postcycloaddition manipulations that could be exploited to synthetic advantage.
Facile construction of novel polycyclic ring systems using a metallocarbenoid-induced cyclization of acetylenic diazo carbonyl compounds
Padwa, Albert,Straub, Christopher S.
, p. 2093 - 2095 (2007/10/03)
equation presented The Rh(II)-catalyzed reaction of diazo 2-propynyl maolonamic acid ester derivatives produce furo[3,4-c]furans in excellent yield. The methodology was applied to the synthesis of several polyheterocyclic systems by first generating a 2-a
