RESUMEN
By using cyclic (vinyl triflate)iodonium salts, a novel triple Suzuki-Miyaura reaction was accomplished for the synthesis of polyaromatic ethylene derivatives in the presence of palladium catalysts. The reaction exhibits extensive compatibility with a wide range of readily available arylboronic acids, giving triaryl-substituted ethylenes in good yields.
RESUMEN
An efficient iron-catalyzed asymmetric [4 + 2] cycloaddition of cyclopentadiene with α,ß-unsaturated acyl imidazoles or 2-cinnamoylisoindoline-1,3-dione derivatives was developed to afford the addition products in high yield and selectivity. Interestingly, the absolute structures of the addition products were controlled by the auxiliaries via different coordination modes with the same type of catalyst.
RESUMEN
[FeIII(TF4DMAP)Cl] can efficiently catalyze intermolecular sp3 C-H amination using aryl azides and intramolecular sp3 C-H amination of alkyl azides in moderate-to-high product yields. At catalyst loading down to 1 mol %, the reactions display high chemo- and regioselectivity with broad substrate scope and are effective for late-stage functionalization of complex natural/bioactive molecules.
RESUMEN
An efficient Fe(TPP)Cl catalyzed insertion reaction of in situ generated benzylic carbenes from N-tosylhydrazones into X-H (X = Si, Sn, Ge) was developed. Silanes bearing tertiary, secondary, and primary (3°, 2°, and 1°) Si-H bonds all reacted well to afford insertion products in moderate to high yields (up to 97%), and the reaction time could be significantly shortened to 1 h under microwave irradiation. A programmable stepwise double insertion strategy was developed for the synthesis of unsymmetrical tetrasubstituted silanes.
RESUMEN
The development of environmentally benign catalysts for highly enantioselective asymmetric cis-dihydroxylation (AD) of alkenes with broad substrate scope remains a challenge. By employing [Fe(II) (L)(OTf)2 ] (L=N,N'-dimethyl-N,N'-bis(2-methyl-8-quinolyl)-cyclohexane-1,2-diamine) as a catalyst, cis-diols in up to 99.8 % ee with 85 % isolated yield have been achieved in AD of alkenes with H2 O2 as an oxidant and alkenes in a limiting amount. This "[Fe(II) (L)(OTf)2 ]+H2 O2 " method is applicable to both (E)-alkenes and terminal alkenes (24 examples >80 % ee, up to 1â g scale). Mechanistic studies, including (18) O-labeling, UV/Vis, EPR, ESI-MS analyses, and DFT calculations lend evidence for the involvement of chiral Fe(III) -OOH active species in enantioselective formation of the two C-O bonds.
RESUMEN
Anti-Markovnikov oxidation of terminal aryl alkenes to aldehydes and transformation of N-methyl aryl tertiary amines to formamides with H2O2 as a terminal oxidant under mild conditions have been achieved with moderate to good product yields using [Fe(III)(TF4DMAP)OTf] as catalyst.
RESUMEN
Chiral iron(iii)-salan complexes catalysed highly enantioselective α-fluorination and α-hydroxylation of ß-keto esters and N-Boc oxindoles to give the corresponding products in high yields and good-to-excellent ee values under mild reaction conditions.
RESUMEN
Chiral dirhodium carboxylate complexes ([Rh(2)(S-PTAD)(4)] or [Rh(2)(S-PTTL)(4)]) efficiently catalyze asymmetric three-component coupling reactions of α-diazophosphonates, anilines, and electron-deficient aldehydes to give α-amino-ß-hydroxyphosphonates. The high level of enantiocontrol provides evidence for the intermediacy of metal-bound ammonium ylide in the product-forming step.
Asunto(s)
Aldehídos/química , Compuestos de Anilina/química , Ácidos Carboxílicos/síntesis química , Organofosfonatos/química , Rodio/química , Compuestos Azo/química , Ácidos Carboxílicos/química , Catálisis , Estructura Molecular , EstereoisomerismoRESUMEN
The chiral iridium porphyrin [Ir((-)-D(4)-Por*)(Me)(EtOH)] displays excellent reactivity and stereoselectivity towards carbene insertion to C-H and Si-H bonds, affording corresponding products in high yields (up to 96%) and high enantioselectivities (up to 98% ee).
Asunto(s)
Carbono/química , Hidrógeno/química , Iridio/química , Metaloporfirinas/química , Metano/análogos & derivados , Silicio/química , Catálisis , Ligandos , Metano/química , Estereoisomerismo , Especificidad por SustratoRESUMEN
[Fe(Por)CF(3)SO(3)] (Por = porphyrin dianion) can efficiently catalyze selective oxidation of terminal aryl alkenes and aliphatic alkenes to aldehydes in good to high yields under mild conditions.
Asunto(s)
Aldehídos/química , Alquenos/química , Hierro/química , Mesilatos/química , Metaloporfirinas/química , Catálisis , Oxidación-Reducción , Especificidad por SustratoRESUMEN
A novel HOTf-catalyzed three-component one-pot cycloaddition of alpha-diazo ester, nitrosobenzene and electron deficient alkene has been developed. This catalysis is very simple to operate and tolerant to moisture/oxygen to afford the product with high to excellent diastereoselectivity in good to excellent yield, thus providing a useful and convenient method for the preparation of diverse functionalized isoxazolidines under very mild conditions.
Asunto(s)
Alquenos/química , Compuestos Nitrosos/química , Catálisis , Cristalografía por Rayos X , Ciclización , Ésteres , Conformación Molecular , EstereoisomerismoRESUMEN
cis-Beta-[Ru(II)(salen(A))(CO)(2)] (salen(A) = N,N'-bis(3-R(1)-5-R(2)-salicylidene)-1,2-cyclohexenediamine dianion; R(1) = R(2) = Bu(t), 1a; R(1) = Pr(i), R(2) = H, 1b; R(1) = Bu(t), R(2) = H, 1c) complexes were prepared by treating Ru(3)(CO)(12) with the respective H(2)salen(A) in 1,2,4-trichlorobenzene and structurally characterized by X-ray crystallography. Complexes 1a-c catalyze intramolecular cyclopropanation of trans-allylic diazoacetates N(2)CHCO(2)CH(2)CH=CHR (3, R = Ph, 4-ClC(6)H(4), 4-BrC(6)H(4), 4-MeC(6)H(4), 4-MeOC(6)H(4), 2-MeC(6)H(4), 2-furanyl) under light irradiation to give cyclopropyl lactones 4 in up to 96% yield and up to 98% ee. DFT calculations on intramolecular cyclopropanation of 3a (R = Ph) with model catalyst cis-beta-[Ru(II)(salen(A0))(CO)(2)] (salen(A0) = N,N'-bis(salicylidene)-1,2-cyclohexenediamine dianion) reveal the intermediacy of both cis-beta- and trans-[Ru(salen(A0))(CHCO(2)CH(2)CH=CHPh)(CO)] bearing salen(A0) in a nonplanar and planar coordination mode, respectively, with the cis-beta-carbene species being a major intermediate in the catalytic carbenoid transfer reaction. The intramolecular cyclopropanation from the cis-beta-carbene species is the most favorable pathway and features an early transition state and an asynchronous concerted [2 + 1] addition mechanism. Enantioselectivities in the reactions involving [Ru(salen(A0))(CHCO(2)CH(2)CH=CHPh)(CO)] were predicted to be 77% ee for the trans-carbene species and 96% ee for the cis-beta-carbene species; the former dramatically increases to 98% ee, whereas the latter slightly increases to 99% ee, upon replacing salen(A0) with salen(A1) (R(1) = R(2) = B(t)). The observed variation in enantioselectivity (90-98% ee) for the conversion of 3a to 4a catalyzed by 1a-c could result from an equilibrium between cis-beta (major) and trans (minor) ruthenium-carbene intermediates.
Asunto(s)
Química Orgánica/métodos , Rutenio/química , Alquenos/química , Carbono/química , Catálisis , Cristalografía por Rayos X/métodos , Hidrógeno , Ligandos , Espectroscopía de Resonancia Magnética , Modelos Químicos , Modelos Moleculares , Conformación Molecular , TermodinámicaRESUMEN
Aryl- and aliphatic-substituted 3-hydroxyprolines and various other amino esters are conveniently prepared by [RuCl2(p-cymene)]2-catalyzed one-pot intramolecular and intermolecular carbenoid N-H insertion reactions, respectively, and the prolines are formed with high diastereoselectivities. The catalytic reactions are tolerant toward air/moisture, and the product yields are insensitive to the organic solvents used.