37810-16-5Relevant academic research and scientific papers
Normal, Leveled, and Enhanced Steric Effects in Alkoxyamines Carrying a β-Phosphorylated Nitroxyl Fragment
Audran, Gérard,Bikanga, Raphael,Brémond, Paul,Joly, Jean-Patrick,Marque, Sylvain R. A.,Nkolo, Paulin
, p. 5702 - 5709 (2017)
The design of new R1R2NOR3 alkoxyamines for various applications relies on the accurate prediction of two kinetic parameters, the C-ON bond homolysis rate constant (kd) and its re-formation rate constant (kc). Relationships to describe the steric and polar effects of the R1R2NO fragment ruling kd have been developed. For all cyclic nitroxyl fragments, the steric effect is described as the sum of the bulkiness of the R1 and R2 groups (i.e., normal steric effect), while for the noncyclic nitroxyl fragment (except for one case), a leveled steric effect is assumed. In this work, we show that the normal steric effect also applies to noncyclic nitroxyl fragments and that for one case an enhanced steric effect is also observed, i.e., experimental kd >5-fold larger than the predicted value.
Modular synthesis of indoles from imines and o-dihaloarenes or o-chlorosulfonates by a Pd-catalyzed cascade process
Barluenga, Jose,Jimenez-Aquino, Agustin,Aznar, Fernando,Valdes, Carlos
supporting information; experimental part, p. 4031 - 4041 (2009/09/04)
A detailed study of the scope of a new Pd-catalyzed synthesis of indolesfrom 1,2-dihaloarenes and o-halobenzene sulfonates and imines is descri bed. The cascade reaction comprises an imine a-arylation ollowed by an intramolecular C-N bond-forming reaction promoted by the same Pd catalyst. The reaction with 1,2-dibromobenzene shows wide scope and allows the introduction of aryl, alkyl, and vinyl substituents at different positions of the five-membered ring of the indole. The regioselective synthesis of indoles substituted in the six-membered ring can be carried out by employing o-dihalobenzene derivatives with two different halogens, taking advantage of the different reactivities of I, Br, and Cl in oxidative addition reactions. This paper also introduces a method for the efficient cleavage of the N-t-butyl group, thus allowing for the preparation of N-H indoles through the same methodology. Finally, the reaction with o-halosulfonates has been studied. The best substrates are o-chlorononaflates, which lead to indoles in very high yield. The reaction is particularlyappropriate for the synthesis of the challenging 6-substituted indoles. In view of the availability of o-chlorophenols, which are direct precur sors of the chlorononaflates, this reaction represents an efficient entry into indoles substituted in the six-membered ring. The concept is illustrated by the preparation of a 4,6-disubstituted indole from naturally occurring anethole.
ON THE DIRECT METALATION OF ISOPRENE
Klusener, P. A. A.,Tip, L.,Brandsma, L.
, p. 2041 - 2064 (2007/10/02)
Isoprene has been metalated in tetrahydrofuran with an excess of sterically hindered potassium dialkylamides, prepared by combining equimolar amounts of the corresponding lithium amide and potassium tert-butoxide.Subsequent reaction with oxirane, alkyl bromides, and pivaldehyde gave the expected coupling products in reasonable yields.Coupling with (CH3)2CHCH2CH=O and (CH3)2C=CHCH=O afforded the bark beetle pheromones (+/-)-ipsenol and (+/-)-ipsdienol in low yields.
Hindered Amines. Synthesis of Hindered Acyclic α-Aminoacetamides
Lai, John T.
, p. 3671 - 3673 (2007/10/02)
Hindered amines and their nitroxyl radicals are useful in spin-label studies as nonnucleophilic bases and as stabilizers for polymers against UV degradation.Hindered acyclic α-aminoacetamides (3, R5 = aryl, tert-butyl; R6 = H) can be synthesized from amines, ketones, and chloroform with 50percent sodium hydroxide solution in phase-transfer-catalyzed reactions.Nucleophilic secondary amines will undergo the same reactions while bulky ones fail.Mixed 3 can be prepared from different amines according to their nucleophilicities. 1,1-Dialkyl-2,2-dichlorooxirane (5) is believedto be the reactive intermediate.Imines are sometimes formed as byproducts through the opening of a carbon-carbon bond in the oxirane ring by amines.Thus, tert-butylcyclohexylamine (7) is obtained in 62percent yield after hydrogenation of the crude imine from tert-butylamine, cyclohexanone, and chloroform.
