Ring expansion by tandem double Tebbe–Claisen technology

1992 ◽  
Vol 70 (5) ◽  
pp. 1356-1365 ◽  
Author(s):  
Leo A. Paquette ◽  
Christophe M. G. Philippo ◽  
Nha Huu Vo
Keyword(s):  
Room Temperature ◽  
Claisen Rearrangement ◽  
Ring Expansion ◽  
Carbonyl Groups ◽  
Kinetic Effect ◽  
Slight Excess ◽  
Form Part ◽  
Structural Assembly ◽  
Swern Oxidation ◽  
Neutral Conditions

2-Cyclohexenone rings that form part of a larger structural assembly are amenable to peracid oxidation with formation of an epoxy lactone. These intermediates are readily transformed under acidic, basic, or neutral conditions to ring-contracted aldehydo lactones, which are then subjected to condensation with a slight excess of Tebbe reagent. These conditions result in methylenation of carbonyl groups and set the stage for operation of a Claisen rearrangement. When the latter is catalyzed by Tribal, the sigmatropic process occurs at room temperature. With systems typified by 17 and 24, the isomerization is complete within 15 min. The presence of a proximate angular methyl group as in 9b, 29, and 37 exerts a retarding kinetic effect. In such examples, a period of 6 h is required to achieve completion. Swern oxidation completes the conversion to the 4-cyclooctenones, where the two carbons stemming from the Tebbe reagent are inserted between the original carbonyl and α-olefinic carbons. The overall process is tolerant of ether functionality and additional sites of unsaturation.

scholarly journals An unusually rapid Claisen rearrangement involving ring expansion

2000 ◽  
pp. 2339-2340 ◽  
Author(s):  
Gianluca Dimartino ◽  
Jonathan M. Percy
Keyword(s):  
Claisen Rearrangement ◽  
Ring Expansion

Advances in Aza-Claisen-Rearrangement-Induced Ring-Expansion Strategies

2017 ◽  
Vol 6 (9) ◽  
pp. 1117-1129 ◽  
Author(s):  
Jong-Wha Jung ◽  
Seok-Ho Kim ◽  
Young-Ger Suh
Keyword(s):  
Claisen Rearrangement ◽  
Ring Expansion ◽  
Expansion Strategies

scholarly journals A Facile Synthesis of Polysubstituted Pyrroles by One-Pot Three-Component Reaction

2012 ◽  
Vol 9 (4) ◽  
pp. 2239-2244 ◽  
Author(s):  
Hossein Anaraki-Ardakani ◽  
Maziar Noei ◽  
Mina Karbalaei-Harofteh ◽  
Shahab Zomorodbakhsh
Keyword(s):  
Room Temperature ◽  
Facile Synthesis ◽  
One Pot ◽  
Pyrrole Derivatives ◽  
Dialkyl Acetylenedicarboxylates ◽  
One Pot Synthesis ◽  
Three Component Reaction ◽  
High Yields ◽  
Neutral Conditions

A new and efficient one-pot synthesis of polysubstituted pyrrole derivatives by three-component reaction between dialkyl acetylenedicarboxylates, triphenylphosphine, 2-aminopyridin derivatives in the presence of arylglyoxals is described. The reactions were performed in dichloromethane at room temperature and neutral conditions and afforded high yields of products.

Solid lithium perchlorate as a powerful catalyst for the synthesis of β-aminoalcohols under solvent-free conditions

2005 ◽  
Vol 83 (5) ◽  
pp. 505-507 ◽  
Author(s):  
Najmodin Azizi ◽  
Mohammad R Saidi
Keyword(s):  
Ring Opening ◽  
Room Temperature ◽  
Lithium Perchlorate ◽  
Solvent Free ◽  
Solvent Free Conditions ◽  
Reaction Proceeds ◽  
Ring Opening Of Epoxides ◽  
Neutral Conditions ◽  
Hindered Amines ◽  
Short Times

Lithium perchlorate catalyzed the ring opening of epoxides with amines to provide the corresponding β-aminoalcohols in excellent yields with high regioselectivity. The reaction proceeds rapidly under mild and neutral conditions and worked well with primary, secondary, aliphatic, aromatic, and hindered amines in short times at room temperature, in the absence of solvent.Key words: epoxide, lithium perchlorate, β-aminoalcohols, solvent-free.

An Efficient Two-Step Protocol for the Isoprenylation of Xanthone at the C2 Position Starting from 1-Fluoroxanthone Derivative

Synlett ◽  
2020 ◽  
Vol 31 (14) ◽  
pp. 1423-1429
Author(s):  
Takashi Matsumoto ◽  
Yuuki Fujimoto ◽  
Chisato Furukawa ◽  
Kanae Takahashi ◽  
Miho Mochizuki ◽  
...  
Keyword(s):  
Silica Gel ◽  
Room Temperature ◽  
Claisen Rearrangement ◽  
High Yield ◽  
Side Chain ◽  
Snar Reaction

The SNAr reaction of 1-fluoroxanthone derivatives with alkoxide of 1,1-dimethylallyl alcohol cleanly afforded the corresponding ethers, which have thus far been unavailable. The obtained ethers underwent the Claisen rearrangement at room temperature by treatment with silica gel in toluene. This two-step protocol provides expeditious and high-yield access to xanthones possessing isoprenyl or the related allylic side chain at the C2 position.

Synthesis of a Stable Compound with Fivefold Bonding Between Two Chromium(I) Centers

Science ◽  
2005 ◽  
Vol 310 (5749) ◽  
pp. 844-847 ◽  
Author(s):  
Tailuan Nguyen ◽  
Andrew D. Sutton ◽  
Marcin Brynda ◽  
James C. Fettinger ◽  
Gary J. Long ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Room Temperature ◽  
Computational Studies ◽  
X Ray Diffraction ◽  
Electron Pairs ◽  
Stable Compound ◽  
X Ray ◽  
Slight Excess ◽  
Stable Species ◽  
Moisture Sensitive

Although in principle transition metals can form bonds with six shared electron pairs, only quadruply bonded compounds can be isolated as stable species at room temperature. Here we show that the reduction of {Cr(μ-Cl)Ar′}2 [where Ar′ indicates C6H3-2,6(C6H3-2,6-Pri2)2 and Pr indicates isopropyl] with a slight excess of potassium graphite has produced a stable compound with fivefold chromium-chromium (Cr–Cr) bonding. The very air- and moisture-sensitive dark red crystals of Ar′CrCrAr′ were isolated with greater than 40% yield. X-ray diffraction revealed a Cr–Cr bond length of 1.8351(4) angstroms (where the number in parentheses indicates the standard deviation) and a planar transbent core geometry. These data, the structure's temperature-independent paramagnetism, and computational studies support the sharing of five electron pairs in five bonding molecular orbitals between two 3d5 chromium(I) ions.

Reaction of dimethoxycarbene with strained cyclic carbonyl compounds

2000 ◽  
Vol 78 (9) ◽  
pp. 1194-1203
Author(s):  
Paul C Venneri ◽  
John Warkentin
Keyword(s):  
Carbonyl Group ◽  
Carbonyl Compounds ◽  
Ring Expansion ◽  
Carbonyl Groups

A cyclopropanone, a cyclopropenone, cyclobutanones, a cyclobutane-1,3-dione, and a cyclobutene-1,2-dione reacted with dimethoxycarbene to afford acetals of the next larger ring by formal insertion of the carbene into a C—C bond α to the carbonyl group. When either of two saturated α-ring carbons could be involved in the process, the ring expansion was selective, affording primarily the product of apparent insertion into the more substituted ring bond. With 2,3-dimethoxycyclobutene-1,2-dione, insertion occurred between the carbonyl groups and with β-propiolactone it occurred at the lactone bond. β-Propiolactam, however, reacted by insertion of the carbene into the N—H bond.Key words: β-propiolactone, cyclobutanone, cyclobutananedione, cyclopropanone, dialkoxycarbene.

scholarly journals Site-selective remote C(sp3)–H heteroarylation of amides via organic photoredox catalysis

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Hui Chen ◽  
Wenjing Fan ◽  
Xiang-Ai Yuan ◽  
Shouyun Yu
Keyword(s):  
Hydrogen Atom ◽  
Room Temperature ◽  
Ph Value ◽  
Metal Free ◽  
Selective Functionalization ◽  
Site Selectivity ◽  
Hydrogen Atom Transfers ◽  
Site Selective ◽  
Neutral Conditions ◽  
Potential Complement

Abstract Radical translocation processes triggered by nitrogen-centered radicals (NCRs), such as 1,5-hydrogen atom transfers (1,5-HAT), demonstrated by the well-established Hofmann-Löffler-Freytag (HLF) reaction, provide an attractive approach for the controllable and selective functionalization of remote inert C(sp3)–H bonds. Here we report an amidyl radical-triggered site-selective remote C(sp3)–H heteroarylation of amides under organic photoredox conditions. This approach provides a mild and highly regioselective reaction affording remote C(sp3)–H heteroarylated amides at room temperature under transition-metal free, weakly basic, and redox-neutral conditions. Non-prefunctionalized heteroarenes, such as purines, thiazolopyridines, benzoxazole, benzothiazoles, benzothiophene, benzofuran, thiazoles and quinoxalines, can be alkylated directly. Sequential and orthogonal C–H functionalization of different heteroarenes by taking advantage pH value or polarity of radicals has also been achieved. DFT calculations explain and can predict the site-selectivity and reactivity of this reaction. This strategy expands the scope of the Minisci reaction and serves as its alternative and potential complement.

Cp*Ir(iii)-catalyzed C–H/N–H functionalization of sulfoximines for the synthesis of 1,2-benzothiazines at room temperature

2018 ◽  
Vol 54 (49) ◽  
pp. 6288-6291 ◽  
Author(s):  
Yogesh N. Aher ◽  
Dhanaji M. Lade ◽  
Amit B. Pawar
Keyword(s):  
Room Temperature ◽  
Bond Functionalization ◽  
Neutral Conditions

The first Cp*Ir(iii)-catalyzed C–H/N–H bond functionalization of sulfoximines with α-diazocarbonyl compounds has been developed for the synthesis of 1,2-benzothiazines under redox-neutral conditions at room temperature.

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