RESUMEN
A ruthenium-catalyzed C-H alkylation/cyclization sequence is presented to prepare silyl indenes with atom and step-economy. This domino reaction is triggered by acyl silane-directed C-H activation, and an aldehyde controlled the following enol cyclization/condensation other than ß-H elimination. The protocol tolerates a broad substitution pattern, and the further synthetic elaboration of silyl indenes allows access to a diverse range of interesting indene and indanone derivatives.
RESUMEN
Acylsilane represents a valuable synthon in synthetic chemistry. We report on ruthenium(ii)-catalyzed ortho-C-H amination of aroylsilanes to provide facile access to synthetically useful imidobenzoylsilanes and tosyl-amidobenzoylsilanes. The protocols, with broad substrate scope and excellent functional group tolerance, are enabled with the weak chelation-assistance of acylsilane via C-H cyclometallation.
RESUMEN
Olefinic C-H functionalization represents an atom- and step economic approach to valuable olefin derivatives from simpler ones, but controlling the selectivity remains a challenge. Remarkable progress has been made in the site-selective C-H functionalization of arenes and alkanes, but there are still limited examples of selective C-H functionalization of olefins presumably due to the lability and easy decomposition of the alkenyl moiety. Chelation-assisted C-H activation represents an efficient protocol for site- and stereo-selective construction of carbon-carbon and carbon-heteroatom bonds. This review highlights recent advances in vicinal- and geminal-group-directed olefinic C-H functionalization, including alkenylation, arylation, alkynylation, alkylation, halogenation, silylation, cyanation and annulation by the formation of exo-/endo-metallocycles. In particular, geminal-group-directed C-H functionalization is covered for the first time, as well as distal-selective alkenyl C-H functionalization under palladium/norbornene cooperative catalysis, which provides novel disconnections in retrosynthetic analysis and represents the future trend in green chemistry.
RESUMEN
A ruthenium-catalyzed [1,2]-Brook rearrangement involved domino sequence is presented to prepare highly functionalized silyloxy indenes with atomic- and step-economy. This domino reaction is triggered by acylsilane-directed C-H activation, and the aldehyde controlled the subsequent enol cyclization/Brook Rearrangement other than ß-H elimination. The protocol tolerates a broad substitution pattern, and the further synthetic elaboration of silyloxy indenes allows access to a diverse range of interesting indene and indanone derivatives.
RESUMEN
A practical and atom-economic protocol for the stereoselective preparation of various 1,4- and 1,3-diene skeletons through iridium-catalyzed directed olefinic C-H allylation and alkenylation of NH-Ts acrylamides in water was developed. This reaction tolerated a wide scope of substrates under simple reaction conditions and enabled successful gram-scale preparation. Furthermore, an asymmetric variant of this reaction giving enantioenriched 1,4-dienes was achieved employing a chiral diene-iridium complex as the catalyst.
RESUMEN
An alkenyl C-H allylation by an exo-palladacycle intermediate is demonstrated, employing unactivated (Z)-alkenes and allyl carbonates. With the use of an 8-aminoquinoline (AQ) derived amide as the directing group, the N,N-bidentate-chelation-assisted C-H activation protocol proceeded under mild and oxidant-free conditions with excellent selectivity. The utility of this approach is demonstrated by the preparative scale, selective conversion of inseparable Z/E alkenes and ready removal of the amide auxiliary to provide the corresponding ester.
RESUMEN
The first cobalt-catalyzed cross-couplings between olefins has been demonstrated to provide C(alkenyl)-H alkenylation and alkylation products, using complex [Cp*Co(CO)I2]. While coupling partner acrylates afforded conjugated dienoates, α,ß-unsaturated ketones led to γ-alkenyl ketones completely, representing a switchable C-H functionalization controlled by different carbonyl groups.
RESUMEN
An iridium-catalyzed C-H allylation of acrylamides with conjugated dienes was developed, using NH-Ts amide as the directing group. The ligand- and additive-free protocol provided a convenient and atom economic synthesis of branched 1,4-diene skeletons, enabling the tolerance of a wide scope of functionalities such as OMe, F, Cl, Br and CF3. The utility of this protocol is also demonstrated by a preparative scale, as well as C-H functionalization of artemisic amide. Furthermore, NH-Ts amide was efficiently removed by methylation and hydrolysis procedures to provide 1,4-dienoic acid.
RESUMEN
A ruthenium-catalyzed C-H alkenylation of aroylsilanes with electron-deficient alkenes was developed, using acylsilane as the directing group. The mild reaction conditions enable the tolerance of a wide scope of functionalities such as OMe, F, Cl, Br and CF3, providing a convenient and highly effective method for the synthesis of styrene derivatives bearing acylsilane. Steroid and heterocycles such as furan and thiophene were also well tolerated. Furthermore, acylsilane was efficiently converted to the corresponding aldehyde or carboxylic acid.
RESUMEN
Cross-coupling reactions of enol carbamates with alkynes or alkenes are reported, using an inexpensive ruthenium catalyst. With the assistance of the directing group OCONMe2, the protocols provide mild, stereo-selective and efficient routes for the preparation of valuable (Z,Z) and (Z,E)-butadiene skeletons.
RESUMEN
A catalytic oxidative cyclization of 2-aminopyridines or 2-aminobenzothiazole with 2-phenoxyacetophenones (a kind of lignin platform compound) was developed, efficiently providing valuable 3-phenoxy imidazo[1,2-a]pyridines or 3-phenoxy benzo[d]imidazo[2,1-b]thiazoles. The reaction was realized under oxygen by simply using inexpensive CuI as the catalyst.
