778640-87-2Relevant academic research and scientific papers
Nitrone Formation by Reaction of an Enolate with a Nitro Group
Shimizu, Hiroaki,Yoshinaga, Kohei,Yokoshima, Satoshi
, p. 2704 - 2709 (2021/04/12)
Ketones with a 2-nitrophenyl group at the α-position were treated with sodium hydroxide in methanol at 60 °C. Under these conditions, enolates derived from the ketones intramolecularly reacted with the nitro group to form a variety of nitrones. Additional experimental results, including the unexpected isolation of N-hydroxyindolinone as a byproduct, led to a proposed reaction mechanism, occurring via an α-hydroxyketone. The resultant nitrones underwent inter- and intramolecular 1,3-dipolar cycloaddition with olefins to afford polycyclic isoxazolidines.
On the mechanism of intramolecular sensitization of photocleavage of the 2-(2-nitrophenyl)propoxycarbonyl (NPPOC) protecting group
Woell, Dominik,Laimgruber, Stefan,Galetskaya, Marina,Smirnova, Julia,Pfleiderer, Wolfgang,Heinz, Bjoern,Gilch, Peter,Steiner, Ulrich E.
, p. 12148 - 12158 (2008/09/17)
A spectroscopic study of a variety of covalently linked thioxanthone(TX)-linker-2-(2-nitrophenyl)-propoxycarbonyl(NPPOC)-substrate conjugates is presented. Herein, the TX chromophore functions as an intramolecular sensitizer to the NPPOC moiety, a photolabile protecting group used in photolithographic DNA chip synthesis. The rate of electronic energy transfer between TX and NPPOC was quantified by means of stationary fluorescence as well as nanosecond and femtosecond time-resolved laser spectroscopy. A dual mechanism of triplet-triplet energy transfer has been observed comprising a slower mechanism involving the T1(ππ*) state of TX with linker-length-dependent time constants longer than 20 ns and a fast mechanism with linker-length-dependent time constants shorter than 3 ns. Evidence is provided that the latter mechanism is due to energy transfer from the T 2(nπ*) state which is in fast equilibrium with the fluorescent S1(ππ*) state. In the case of direct linkage between the aromatic rings of TX and NPPOC, the spectroscopic properties are indicative of one united chromophore which, however, still shows the typical NPPOC cleavage reaction triggered by intramolecular hydrogen atom transfer to the nitro group.
Diastereoselective synthesis of substituted 2,3,4,5-tetrahydro-1H-1- benzazepine-5-carboxylic esters by a tandem reduction-reductive amination reaction
Bunce, Richard A.,Johnson, Lara B.,Holt, Elizabeth M.
, p. 563 - 568 (2007/10/03)
An efficient, diastereoselective synthesis of substituted and unsubstituted 2,3,4,5-tetrahydro-1H-1-benzazepine-5-carboxylic esters has been developed based on the tandem reduction-reductive animation reaction. Catalytic hydrogenation of a series of 2-(2-nitrophenyl)-5-oxoalkanoic esters initiates a reaction sequence involving (1) reduction of the aromatic nitro group, (2) condensation of the N-hydroxylamino (or amino) nitrogen with the side chain carbonyl, and (3) reduction of the seven-membered cyclic imine. Cyclizations that produce 2-alkyl-2,3,4,5-tetrahydro-1H-1-benzazepine-5-carboxylic esters are diastereoselective for the product having the C2 alkyl and the C5 ester groups cis. In these reactions, the transannular ester group exerts a strong seediest effect on the reduction of the cyclic imine intermediate, though not as strong as that observed in previous closures of 2-alkyl-1,2,3,4-tetrahydroquinoline-4- carboxylic esters. This decrease in diastereoselectivity is attributed to (1) the greater distance between the ester and the imine double bond and (2) the increased conformational mobility of the larger ring, both of which diminish the stereodirecting effect of the ester. Finally, formation of the seven-membered ring is sufficiently slow that reaction with the side chain ester group competes with heterocycle formation in several of the reactions.
