1775-74-2Relevant articles and documents
Beyond the five and six: Evaluation of seven-membered cyclic anhydrides in the castagnoli-cushman reaction
Adamovskyi, Mykhailo I.,Ryabukhin, Sergey V.,Sibgatulin, Dmitriy A.,Rusanov, Eduard,Grygorenko, Oleksandr O.
, p. 130 - 133 (2017)
The Castagnoli-Cushman reaction with benzo[d]- oxepine-2,4(1H,5H)-dione as an anhydride component allowed for preparation of 2,3-disubstituted 4-oxo-2,3,4,5-tetrahydro-1H-benzo[d]- azepine-1-carboxylic acids in 21-75% yields and with good trans diastereoselectivity. The method worked with imines generated from aromatic or a-branched aliphatic aldehydes and is amenable for both parallel synthesis and scale-up. The procedure for epimerization of the resulting trans-disubstituted tetrahydrobenzo[d]azepines to their cis isomers was also developed.
Enantioselective Reductive Cyanation and Phosphonylation of Secondary Amides by Iridium and Chiral Thiourea Sequential Catalysis
Chen, Dong-Huang,Sun, Wei-Ting,Zhu, Cheng-Jie,Lu, Guang-Sheng,Wu, Dong-Ping,Wang, Ai-E,Huang, Pei-Qiang
supporting information, p. 8827 - 8831 (2021/03/16)
The combination of transition-metal catalysis and organocatalysis increasingly offers chemists opportunities to realize diverse unprecedented chemical transformations. By combining iridium with chiral thiourea catalysis, direct enantioselective reductive cyanation and phosphonylation of secondary amides have been accomplished for the first time for the synthesis of enantioenriched chiral α-aminonitriles and α-aminophosphonates. The protocol is highly efficient and enantioselective, providing a novel route to the synthesis of optically active α-functionalized amines from the simple, readily available feedstocks. In addition, the reactions are scalable and the thiourea catalyst can be recycled and reused.
A BEt3-Base Catalyst for Amide Reduction with Silane
Yao, Wubing,Fang, Huaquan,He, Qiaoxing,Peng, Dongjie,Liu, Guixia,Huang, Zheng
, p. 6084 - 6093 (2019/05/24)
Reported herein is the development of a simple but practical catalytic system for the selective reduction of amides with hydrosilane or hydrosiloxane. Low-cost and readily available triethylborane (1.0 M in THF), in combination with a catalytic amount of an alkali metal base, was found to catalyze the reduction of all three amide classes (tertiary, secondary, and primary amides) to form amines under mild conditions. In addition, the selective transformation of secondary amides to aldimines and primary amides to nitriles can also be achieved by using a proper combination of BEt3 and base. The scope of these BEt3-base-catalyzed amide hydrosilylation reactions has been explored in depth. Preliminary results of mechanistic studies suggest a modified Piers' silane Si-H···B activation mode wherein the hydride abstraction by BEt3 is promoted by the coordination of an alkoxide or hydroxide anion to the Si center.
Activation of primary amines by copper(i)-based lewis acid promoters in the solventless synthesis of secondary propargylamines
Cimarelli, Cristina,Navazio, Federica,Rossi, Federico V.,Del Bello, Fabio,Marcantoni, Enrico
, p. 2387 - 2396 (2019/05/27)
Primary amines are activated by copper(I)-based Lewis acid promoters in an A 3 -coupling one-pot solventless reaction with aldehydes and phenylacetylene for the synthesis of secondary propargylamines. The reaction is promoted by a CuSO 4 /NaI system, a practical precursor of the in situ generated effective CuI/I 2 system, that worked well, but only in a restricted number of examples. Substitution of I 2 with CeCl 3 ·7H 2 O in a one-pot two-step reaction provided good yields and a wider applicability, with the added value given by a safer procedure.
A BEt3-Base catalyst for amide reduction with silane
Yao, Wubing,Fang, Huaquan,He, Qiaoxing,Peng, Dongjie,Liu, Guixia,Huang, Zheng
, (2019/05/22)
Reported herein is the development of a simple but practical catalytic system for the selective reduction of amides with hydrosilane or hydrosiloxane. Low-cost and readily available triethylborane (1.0 M in THF), in combination with a catalytic amount of an alkali metal base, was found to catalyze the reduction of all three amide classes (tertiary, secondary, and primary amides) to form amines under mild conditions. In addition, the selective transformation of secondary amides to aldimines and primary amides to nitriles can also be achieved by using a proper combination of BEt3 and base. The scope of these BEt3-base-catalyzed amide hydrosilylation reactions has been explored in depth. Preliminary results of mechanistic studies suggest a modified Piers' silane Si-H···B activation mode wherein the hydride abstraction by BEt3 is promoted by the coordination of an alkoxide or hydroxide anion to the Si center.
Zinc(II)-Catalyzed Synthesis of Propargylamines by Coupling Aldimines and Ketimines with Alkynes
Shehzadi, Syeda Aaliya,Saeed, Aamer,Lemière, Filip,Maes, Bert U. W.,Abbaspour Tehrani, Kourosch
supporting information, p. 78 - 88 (2018/03/27)
A ZnII-catalyzed reaction between imines, which were derived from unactivated aldehydes or ketones and primary amines or α-amino acid esters, and terminal alkynes has led to the rapid and efficient formation of tri- and tetrasubstituted propargylamines (from aldimines and ketimines, respectively) in good to excellent yields. No additives or extra Lewis acid reagents were required for the imine-alkyne coupling reaction.
One-Pot Reductive Allylation of Amides by Using a Combination of Titanium Hydride and an Allylzinc Reagent: Application to a Total Synthesis of (-)-Castoramine
Itabashi, Suguru,Shimomura, Masashi,Sato, Manabu,Azuma, Hiroki,Okano, Kentaro,Sakata, Juri,Tokuyama, Hidetoshi
supporting information, p. 1786 - 1790 (2018/07/03)
A one-pot direct reductive allylation protocol has been developed for the synthesis of secondary amines by using titanium hydride and an allylzinc reagent. This protocol is applicable to a broad range of substrates, including acyclic amides, benzamides, α,β-unsaturated amides, and lactams. The stereochemical outcome obtained from the reaction with crotylzinc reagent suggested that the allylation reaction proceeds through a six-membered cyclic transition state. A total synthesis of (-)-castoramine was accomplished by following this protocol for the highly stereoselective construction of contiguous stereocenters.
Aza-Henry reactions on C-Alkyl substituted aldimines
Pelagalli, Alessia,Pellacani, Lucio,Scandozza, Elia,Fioravanti, Stefania
, (2016/07/07)
The reactivity of C-CH3 substituted N-protected aldimines in aza-Henry addition reactions was compared with that of the analogous trifluoromethylated compounds. C-Alkyl aldimines easily reacted with nitro alkanes under solvent-free conditions and in the absence of catalyst, despite being worse electrophiles than C-CF3 aldimines, they gave the aza-Henry addition only when ZrCl4 was added. The presence of a bulky group on the imine carbon deeply influenced the reactivity.
Factors influencing the regioselectivity of the oxidation of asymmetric secondary amines with singlet oxygen
Ushakov, Dmitry B.,Plutschack, Matthew B.,Gilmore, Kerry,Seeberger, Peter H.
supporting information, p. 6528 - 6534 (2015/04/22)
Aerobic amine oxidation is an attractive and elegant process for the α functionalization of amines. However, there are still several mechanistic uncertainties, particularly the factors governing the regioselectivity of the oxidation of asymmetric secondary amines and the oxidation rates of mixed primary amines. Herein, it is reported that singlet-oxygen-mediated oxidation of 1° and 2° amines is sensitive to the strength of the α-C-H bond and steric factors. Estimation of the relative bond dissociation energy by natural bond order analysis or by means of one-bond C-H coupling constants allowed the regioselectivity of secondary amine oxidations to be explained and predicted. In addition, the findings were utilized to synthesize highly regioselective substrates and perform selective amine cross-couplings to produce imines.
Semi-catalytic reduction of secondary amides to imines and aldehydes
Lee, Sun-Hwa,Nikonov, Georgii I.
supporting information, p. 8888 - 8893 (2014/06/09)
Secondary amides can be reduced by silane HSiMe2Ph into imines and aldehydes by a two-stage process involving prior conversion of amides into iminoyl chlorides followed by catalytic reduction mediated by the ruthenium complex [Cp(i-Pr3P)Ru(NCCH3)2]PF6 (1). Alkyl and aryl amides bearing halogen, ketone, and ester groups were converted with moderate to good yields under mild reaction conditions to the corresponding imines and aldehydes. This procedure does not work for substrates bearing the nitro-group and fails for heteroaromatic amides. In the case of cyano substituted amides, the cyano group is reduced to imine.
