Regio- and stereochemical course of the ring expansion of bridged bicyclic ketones to spirocyclic .alpha.-keto tetrahydrofurans.

1992 ◽  
Vol 57 (14) ◽  
pp. 3956-3965 ◽  
Author(s):  
Leo A. Paquette ◽  
John F. P. Andrews ◽  
Corinne Vanucci ◽  
David E. Lawhorn ◽  
Joanna T. Negri ◽  
...  
Keyword(s):  
Ring Expansion ◽  
Bicyclic Ketones

ChemInform Abstract: Regio- and Stereochemical Course of the Ring Expansion of Bridged Bicyclic Ketones to Spirocyclic α-Keto Tetrahydrofurans.

ChemInform ◽  
1992 ◽  
Vol 23 (51) ◽  
pp. no-no
Author(s):  
L. A. PAQUETTE ◽  
J. F. P. ANDREWS ◽  
C. VANUCCI ◽  
D. E. LAWHORN ◽  
J. T. NEGRI ◽  
...  
Keyword(s):  
Ring Expansion ◽  
Bicyclic Ketones

13C magnetic resonance studies. 124. Preparative ring expansions of bicyclic ketones by homoketonization of cyclopropoxide analogs

1986 ◽  
Vol 64 (7) ◽  
pp. 1390-1399 ◽  
Author(s):  
Vijay Patel ◽  
Arthur J. Ragauskas ◽  
J. B. Stothers
Keyword(s):  
Magnetic Resonance ◽  
Ring Expansion ◽  
Synthetic Method ◽  
Expansion Process ◽  
Enol Ethers ◽  
Magnetic Resonance Studies ◽  
Silyl Ethers ◽  
Silyl Enol Ethers ◽  
Ring Expansions ◽  
Bicyclic Ketones

Homoketonization of some readily prepared cyclopropoxides provides a new synthetic method for ring expansion of the [2.2.1] and [2.2.2] ring systems. Cyclopropanation of the trimethylsilyl enol ethers derived from a variety of polycyclic ketones affords the required cyclopropyl silyl ethers, which may be ketonized directly or hydrolyzed to the corresponding cyclopropanols before ketonization. The results for fourteen examples serve to define the scope of the ring expansion process, and the silyl enol ethers, cyclopropyl silyl ethers, and most of the corresponding cyclopropanols have been characterized by 13Cmr. The stereochemistry of the ketonization leading to ring expansion has been established by deuterium labelling experiments.

A new preparative ring expansion for bicyclic ketones. Homoketonization of cyclopropoxide analogs

1980 ◽  
Vol 58 (23) ◽  
pp. 2730-2732 ◽  
Author(s):  
Yumiko Hoyano ◽  
Vijay Patel ◽  
J. B. Stothers
Keyword(s):  
Ring Expansion ◽  
Synthetic Method ◽  
Ring Systems ◽  
Bicyclic Ketones

Homoketonization of some readily prepared cyclopropoxides affords a new synthetic method for ring expansion of the [2.2.1] and [2.2.2] ring systems.

Synthesis, Structure and Reactivities of Pentacoordinated Phosphorus–Boron Bonded Compounds

2020 ◽  
Author(s):  
Nathan O'Brien ◽  
Naokazu Kano ◽  
Nizam Havare ◽  
Ryohei Uematsu ◽  
Romain Ramozzi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ring Expansion ◽  
Bicyclic Compound ◽  
Compound A ◽  
Ligand System ◽  
Large Bulk ◽  
Rearrangement Reaction ◽  
Hydride Abstraction ◽  
Pentacoordinated Phosphorus ◽  
Acids And Bases

<div>The isolation and reactivities of two pentacoordinated phosphorus–tetracoordinated boron bonded compounds were</div><div>explored. A strong Lewis acidic boron reagent and electron-withdrawing ligand system were required to form the</div><div>pentacoordinated phosphorus state of the P–B bond. The first compound, a phosphoranyl-trihydroborate, gave a THF</div><div>stabilised phosphoranyl-borane intermediate upon a single hydride abstraction in THF. This compound could undergo a</div><div>unique rearrangement reaction, that involved a two-fold ring expansion, to give an unusual fused bicyclic compound or it</div><div>could act as a mono-hydroboration reagent. The hydroboration reactivity of the intermediate was found to be more reactive</div><div>towards alkynes over alkenes with good to moderate regioselectivity towards the terminal carbon. The second compound,</div><div>a phosphoranyl-triarylborate, was found to have a vastly different reactivity to the trihydroborate as it was highly stable</div><div>towards acids and bases. This is thought to be due to the large bulk around the P–B bond as shown in the crystal structure</div>

Concise Synthesis of GB22 by Endo-Selective Siloxycyclopropane Arylation

2019 ◽  
Author(s):  
Hannah E. Burdge ◽  
Takuya Oguma ◽  
Takahiro Kawajiri ◽  
Ryan Shenvi
Keyword(s):  
Intramolecular Cyclization ◽  
Cross Coupling ◽  
Building Blocks ◽  
Ring Expansion ◽  
Dual Catalysis ◽  
Acid Labile

<div><div><div><p>The first synthesis of GB22 was accomplished by a con- cise, modular route. Two building blocks converged in a novel sp3-sp2 attached-ring coupling that used Ir/Ni dual-catalysis to reverse the regioselectivity of siloxycy- clopropane arylation. This cross-coupling proved general to access β-substituted tetralones via ring-expansion of indanone-derived siloxycyclopropanes. The congested, bridging rings of the GB alkaloids were completed using an aluminum-HFIP complex that effected intramolecular cyclization of an acid-labile substrate.</p></div></div></div>

Concise Synthesis of GB22 by Endo-Selective Siloxycyclopropane Arylation

2019 ◽  
Author(s):  
Hannah E. Burdge ◽  
Takuya Oguma ◽  
Takahiro Kawajiri ◽  
Ryan Shenvi
Keyword(s):  
Intramolecular Cyclization ◽  
Cross Coupling ◽  
Building Blocks ◽  
Ring Expansion ◽  
Dual Catalysis ◽  
Acid Labile

<div><div><div><p>The first synthesis of GB22 was accomplished by a con- cise, modular route. Two building blocks converged in a novel sp3-sp2 attached-ring coupling that used Ir/Ni dual-catalysis to reverse the regioselectivity of siloxycy- clopropane arylation. This cross-coupling proved general to access β-substituted tetralones via ring-expansion of indanone-derived siloxycyclopropanes. The congested, bridging rings of the GB alkaloids were completed using an aluminum-HFIP complex that effected intramolecular cyclization of an acid-labile substrate.</p></div></div></div>

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