Extremely Regioselective Intramolecular Silylformylation of Alkynes

Ojima, Iwao; Vidal, Ephraim S.; Tzamarioudaki, Maria; Matsuda, Isamu

doi:10.1021/ja00130a027

Cited by 71 publications

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“…[19] Many different catalysts were found to be effective in the silylformylation of alkynes. Rh I and Rh II species [22] and RhϪCo mixed complexes such as (tBuNC) 4 RhCo(CO) 4 [23] and Co 2 Rh 2 (CO) 12 [24] have been reported to be highly reactive. Rh 4 (CO) 12 is the most commonly used catalyst, [25] even if it sometimes displays lower chemoselectivity [19] (hydrosilylation vs. silylformylation).…”

Section: Introductionmentioning

confidence: 99%

Silylformylation of Chiral 1-Alkynes, Catalysed by Solvated Rhodium Atoms

Aronica¹,

Terreni²,

Caporusso³

et al. 2001

Eur. J. Org. Chem.

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Solvated rhodium atoms, prepared by the metal vapour synthesis technique, promote the silylformylation reaction of variously substituted alkynes R 1 R 2 CH(CH 2 ) n CϵCH, with catalytic activities comparable with and even higher than more common species such as Rh 4 (CO) 12 . Z-Silylalkenals are exclusively formed in high yields (60−95%) indicating syn addition both of CO and of the silane (Me 2 PhSiH) to the triple bond. The chemoselectivity of the process (silylformylation vs. hydrosilylation) is highly affected by the amount of cata-

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Section: Introductionmentioning

confidence: 99%

Silylformylation of Chiral 1-Alkynes, Catalysed by Solvated Rhodium Atoms

Aronica¹,

Terreni²,

Caporusso³

et al. 2001

Eur. J. Org. Chem.

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“…Various functional groups, e.g., ether, ester, hydroxyl, and sulfonamide, and heteroatoms in the backbone of enediynes 14 are well tolerated in this reaction to give the corresponding fused 5-7-5 tricyclic products 15 in good to excellent isolated yields [10]. Other rhodium catalysts, Rh(acac)(CO) 2 , Rh 4 (CO) 12 , and [Rh(CO) 2 Cl] 2 , show similar efficacy. As hydrosilane, PhMe 2 SiH is the best, but Ph 2 MeSiH, (EtO) 3 SiH, and Et 3 SiH can also be used.…”

Section: Carbonylative Carbotricyclization Of Enediynesmentioning

confidence: 94%

“…1) [1][2][3]. The SiCaC reaction of 1,6-enynes is catalyzed by Rh 4 (CO) 12 (1) which enable the reaction to proceed at ambient temperature and completes mostly within a minute. Other Rh catalysts such as Rh(acac)(CO) 2 are also effective for this reaction, but require 65-70 °C to promote the reaction efficiently.…”

Section: Silylcarbocyclizations (Sicacs)mentioning

confidence: 99%

“…Indeed, the reaction of dodeca-1,6,11-triyne 6 [X = C(CO 2 Et) 2 ] under the standard SiCaC conditions using Rh(acac)(CO) 2 as the catalyst and PhMe 2 SiH as the hydrosilane at 70 °C gave a 2:2:1 mixture of 7, 8, and 9 in 94% total yield, achieving the first silylcarbotricyclization (SiCaT) via three consecutive carbocyclizations (Scheme 1) [8]. Under optimized conditions using Rh 4 (CO) 12 as the catalyst and 2 equiv of hydrosilane to 6 at 22 °C, fused tricyclic silylbenzene 7 was obtained in excellent yield with 84-93% selectivity. Several Rh complexes were found to be effective in the SiCaT reaction, which are Rh(acac)(CO) 2 nitrogen atoms in the backbone are proven to be good substrates for this process.…”

Section: Cascade Silylcarbocyclizationsmentioning

confidence: 99%

“…Accordingly, the intramolecular directed silylformylation has been developed to obtain the products with opposite regiochemistry as well as to achieve complete regio-control. For example, the reactions of ω-dimethylsiloxyalkynes 17 and 19 catalyzed by Rh and Rh-Co complexes proceed via exo-dig cyclization to give the corresponding 5-exo-formylalkylideneoxasilacycloalkanes 18 and 20, respectively, in excellent yields (Scheme 5) [12]. This reaction is applicable to ω-disilylaminoalkynes, which gives aza-1-silacyclopentanes, e.g., 21 → 22 [13].…”

Section: Desymmetrization Of Hydrosiloxyalkadiynes By Intramolecular mentioning

confidence: 99%

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New cyclization reactions in organic syntheses

Ojima

2002

Pure and Applied Chemistry

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Recent development in the transition metal-catalyzed cyclization reactions for organic syntheses in the author's laboratories is summarized, which includes (i) novel silylcarbocyclizations (SiCaCs) and carbonylative carbotricyclizations, (ii) intramolecular silylformylations and desymmerization of siloxydiynes by sequential double silylformylation, (iii) efficient total synthesis of (+)-prosopinine, (iv) enantioselective desymmetrization of aminodienes, and (iv) new and efficient routes to 1-azabicyclo[x.y.0]alkane amino acids. All these processes are catalyzed by Rh or Rh-Co complexes, and useful for rapid and efficient construction of a variety of heterocyclic and carbocyclic compounds. Mechanisms of these new carbocyclization and cyclohydrocarbonylation reactions are also discussed.It has been the central focus in modern organic synthesis to develop highly efficient catalytic processes for the syntheses of natural and unnatural compounds of medicinal interest or intermediates useful for functional materials. One of the most attractive approaches to such aims is to apply transition metal-catalyzed cyclization reactions for the transformations of simple starting materials into monocyclic, bicyclic, and polycyclic scaffolds that can be further elaborated into specific targets.This account describes new and useful cyclization processes based on silylcarbocyclization (SiCaC), silylformylation, and cyclohydrocarbonylation reactions, which have recently been developed in these laboratories and will find many applications in organic syntheses. SILYLCARBOCYCLIZATIONS (SiCaCs)The first silylcarbocyclization was discovered serendipitously during our detailed product analysis of the silylformylation of 1-hexyne catalyzed by Rh and Rh-Co carbonyl clusters, which gave dibutylcyclopentenone by incorporating two molecules of 1-hexyne, one molecule of hydrosilane, and one molecule of CO. Following up this discovery, we have investigated the intramolecular version of this reaction using a variety of 1,6-enynes, which led to the discovery of novel silylcarbocyclization (SiCaC) reaction (eq. 1) [1][2][3]. The SiCaC reaction of 1,6-enynes is catalyzed by Rh 4 (CO) 12 and Rh 2 Co 2 (CO) 12 , *Lecture presented at the

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