Unsaturated heterocyclic systems. XCIV. Response of homo- and benzhomobarrelenes to uniparticulate electrophilic attack. Effect of a lateral cyclopropane ring on the direction and stereochemistry of chlorosulfonyl isocyanate addition

Volz, William E.; Paquette, Leo A.

doi:10.1021/jo00863a013

Cited by 13 publications

(7 citation statements)

References 7 publications

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“…In order to test this hypothesis we reacted the carbocyclic analog 32 with Pd(OAc) 2 -CH 2 N 2 and found that the benzobicyclo[2.2.2] system in 32 was cyclopropanated exclusively from the face proximal to the benzene ring ( endo ) to give 33 as the sole product. [15] These results corroborate the findings of Anciaux, Hubert et al that Pd catalyzed cyclopropanations are exceedingly sensitive to the steric effects of the substrate. [16] …”

supporting

confidence: 89%

Palladium‐Catalyzed Cyclopropanation of Unsaturated Endoperoxides. A New Peroxide‐Preserving Reaction

Emerzian

Davenport²,

Song³

et al. 2009

Adv Synth Catal

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Unsaturated bicyclic endoperoxides are efficiently cyclopropanated with excess diazomethane in the presence of catalytic Pd(OAc)2 in a stereoselective manner. This method represents a new peroxide preserving transformation. Whereas the unsaturated endoperoxides in the [2.2.1] series are attacked by the carbene from the exo face, the analogs with larger bridges are preferentially attacked from the face syn to the peroxo bridge. Only in the case of the benzannelated [2.2.2] system the attack occurs exclusively from the face proximal to the benzene ring. Certain strained cyclopropanated endoperoxides are reduced by diazomethane to give cis-diols. 1-Methylfuran endoperoxide gives rise to cis-1-formyl-2-acetylcyclopropane in excellent yield.

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supporting

confidence: 89%

Palladium‐Catalyzed Cyclopropanation of Unsaturated Endoperoxides. A New Peroxide‐Preserving Reaction

Emerzian

Davenport²,

Song³

et al. 2009

Adv Synth Catal

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“…Under both conditions, only the N-H insertion product was observed by GC-MS and 1 H NMR. The preference for X-H insertion over cyclopropanation has been previously reported for ruthenium catalyzed N-H and S-H insertions, 9b a rhodium catalyzed O-H insertion, 16 and iron porphyrin and iron corrole catalyzed N-H insertions. 13…”

Section: Resultsmentioning

confidence: 54%

“…Furthermore, a new chemical shift at 4.24 (m, 2H) ppm is consistent with bridgehead protons as reported previously for benzhomobarrelene compounds. 16 The existence of a mirror plane in the product ruled out [2+4] addition of benzyne to the cycloheptatriene form of the valence isomers. Moreover, all [2+2] adducts can be ruled out by the presence of bridgehead protons in the product.…”

Section: Resultsmentioning

confidence: 99%

“…1 values. 15,16 Para product 10 1 H NMR (300 MHz) δ: 7.35 (br, 4H, aryl-H), 4.63 (s, 1H, methine-CH), 3.78 (s, 6H, OCH 3 ). 13 C NMR (75.4 MHz) δ: 168.…”

Section: Methodsmentioning

confidence: 99%

“…[9][10][11][12][13][14] The electrophilicity of the metal-carbene intermediate has been found to have a great influence on the chemo-, regio-, and stereoselectivity of the C-H activation reaction. [15][16][17][18][19] This electrophilicity stems not only from the effect of the associated ligated metal complex 17,18 but also from the substituents on the carbene carbon. [20][21][22][23][24] The nature of the substituents attached to the carbonyl group and identity of the additional substituent at the carbene carbon can dramatically influence the stability of the carbene complex.…”

Section: Porphyrin Ring Introductionmentioning

confidence: 99%

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Novel catalysis by metalloporphyrins

Mbuvi

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Introduction Results and Discussion Conclusion Experimental section References GENERAL CONCLUSION ACKNOWLEDGEMENTS Related to porphyrins are corrins, chlorins (2,3-dihydroporphyrin) and bacteriochlorophylls (2,3,12,13-tetrahydroporphyrin). All of them follow the Hückel 4n+2 rule and hence have aromatic properties. Porphyrins combine readily with metals to form tetrachelate complexes. Iron in hemes, magnesium in chlorophyll, zinc, copper, nickel, and cobalt-containing porphyrins are known, and many other metals porphyrins have been synthesized. A porphyrin in which no metal is inserted in its cavity is called a free base. Some iron-containing porphyrins (heme-containing proteins or hemoproteins) are found extensively in nature, e.g., hemoglobin. Hemoglobin iron is the actual binding site for dioxygen. This iron site can be preferentially bound by carbon monoxide leading to poisoning by asphyxiation. Some shellfish with green-colored blood have a coppercentered porphyrin. If one of the four pyrrole subunits is reduced to pyrroline, a chlorin is produced, which is the ring structure found in chlorophyll. If two of the four pyrrole subunits are reduced, then either a bacteriochlorin (as found in some photosynthetic bacteria) or an isobacteriochlorin is formed, depending on the relative positions of the reduced pyrroles. Metalloporphyrins as Catalysts Metalloporphyrins have long been used as catalysts due to their robust nature and ability to impart unique stereoselectivity to the products. Manganese, iron and ruthenium porphyrins are extensively used as oxidation catalysts. Iron porphyrins have been found to be efficient catalyst for cyclopropanation and olefination of alkenes. The present work focuses on the use of iron porphyrins for N-H, C-H and O-H insertions reactions and cyclopropanation of arenes.

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