Rhodium-Catalyzed Intramolecular Silylcarbotricyclization (SiCaT) of Triynes

Ojima, Iwao; Vu, A. T.; McCullagh, James V.; Kinoshita, Atsushi

doi:10.1021/ja9815529

Cited by 56 publications

(32 citation statements)

References 12 publications

(6 reference statements)

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“…It was anticipated, therefore, that restricting the rotational freedom of the C-C bond connecting two cyclopentyl moieties by incorporating a double bond would make the third carbocyclization possible [8]. 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].…”

Section: Cascade Silylcarbocyclizationsmentioning

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.…”

Section: Cascade Silylcarbocyclizationsmentioning

confidence: 99%

“…A proposed mechanism for the SiCaT reaction is illustrated in Scheme 2, which includes initial insertion of an alkyne moiety of 6 into the Si-[Rh] bond of the active catalyst species followed by three consecutive carbometallations [8]. Deuterium labeling experiment confirmed the cascade process and eliminated the involvement of any common metallacycle in the catalytic cycle.…”

Section: Cascade Silylcarbocyclizationsmentioning

confidence: 99%

“…The formation of the non-silyl product 8 is explained by the occurrence of the Ojima-Crabtree-type rearrangement The SiCaT reaction is applicable to the construction of 6-6-5 and 6-6-6 fused tricyclic skeletons such as 11 and 12 (eq. 4) [8]. Since the formation of 6-membered ring other than benzene ring by catalytic carbocyclization is demanding in general, the ability to construct such ring systems is synthetically significant and advantageous.…”

Section: Cascade Silylcarbocyclizationsmentioning

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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Section: Cascade Silylcarbocyclizationsmentioning

confidence: 99%

Section: Cascade Silylcarbocyclizationsmentioning

confidence: 99%

Section: Cascade Silylcarbocyclizationsmentioning

confidence: 99%

Section: Cascade Silylcarbocyclizationsmentioning

confidence: 99%

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New cyclization reactions in organic syntheses

Ojima

2002

Pure and Applied Chemistry

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“…In the case of alkatriynes 3, however, silylcarbotricyclization (SiCaT) took place to give the fused tricyclic compounds 4a and 4b in good to excellent yields (Scheme 2) 21 Reactions catalyzed by rhodium carbonyl clusters showed high selectivity to 4a.…”

Section: Introductionmentioning

confidence: 99%

Silicon‐Initiated Carbonylative Carbotricyclization and [2 + 2 + 2 +1] Cycloaddition of Enediynes Catalyzed by Rhodium Complexes.

et al. 2006

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The reaction of dodec-11-ene-1,6-diynes or their heteroatom congeners with a hydrosilane catalyzed by Rh(acac)(CO) 2 at ambient temperature and pressure of CO gives the corresponding fused 5-7-5 tricylclic products, 5-oxo-1,3a,4,5,7,9-hexahydro-3H-cyclopenta[e]azulenes or their heteroatom congeners, in excellent yields through a unique silicon-initiated cascade carbonylative carbotricyclization (CO-SiCaT) process. It has also been found that the 5-7-5 fused tricyclic products can be obtained from the same type of enediynes and CO through a novel intramolecular [2+2+2+1] cycloaddition process. The characteristics of these two tricyclization processes and fundamental differences in their reaction mechanisms are discussed. This novel higher-order cycloaddition reaction has also been successfully applied to the tricyclization of undeca-5,10-diyn-1-als, affording the corresponding 5-7-5 fused ring products bearing a 7-membered lactone moiety. Related [2+2+2] tricyclizations of enediyne and diynal substrates are also discussed. These newly discovered reactions can construct multiple bonds all at once, converting linear starting materials to polycyclic compounds in single step. Thus, these new processes provide innovative routes to functionalized polycyclic compounds that are useful for the syntheses of natural and unnatural products.

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