A Model Compound for Anhydroryanodol

1972 ◽  
Vol 50 (24) ◽  
pp. 4013-4021 ◽  
Author(s):  
Brian G. Brownlee ◽  
Pak-Tsun Ho ◽  
K. Wiesner
Keyword(s):  
Double Bond ◽  
Model Compound ◽  
Membered Ring ◽  
Exocyclic Double Bond

The synthesis of the acetoxy lactone 17 by a method potentially suitable for anhydroryanodine is described. In the course of the synthesis several mechanistically unusual reactions were observed. One of them was an attack of Cl+ on an exocyclic double bond in a benzobicycloheptane system from the endo side. Another was a SN2 type displacement of chlorine by chloride or acetate ions in a six-membered ring.

scholarly journals Chemoselective Ring-Opening Polymerization of Bio-Renewable α-Methylene-γ-Butyrolactone via an Organophosphazene/urea Binary Synergistic Catalytic System Toward a Sustainable Polyester

2020 ◽  
Author(s):  
Yong Shen ◽  
Wei Xiong ◽  
YongZheng Li ◽  
ZhiChao Zhao ◽  
Hua Lu ◽  
...  
Keyword(s):  
Double Bond ◽  
Catalytic System ◽  
Low Temperatures ◽  
Ring Opening ◽  
Theoretical Calculations ◽  
Unsaturated Polyester ◽  
Ring Opening Polymerization ◽  
Membered Ring ◽  
Exocyclic Double Bond ◽  
Binary Catalyst

Despite the great potential of bio-renewable a-methylene-<a></a><a></a><a>g-butyrolactone</a> (MBL) to produce functional recyclable polyester, the ring-opening polymerization (ROP) of MBL remains as a challenge due to the competing polymerization of the highly reactive exocyclic double bond and the low strained five membered ring. In this contribution, we present the first organocatalytic chemoselective ROP of MBL to exclusively produce recyclable unsaturated polyester by utilizing a phosphazene base/urea binary catalyst. We show that delicate chemoselectivity can be realized by controlling the temperature and using selected urea catalysts. Experimental and theoretical calculations provide mechanistic insights and indicate that the kinetically controlled ROP pathway is favored by using urea with stronger acidity at low temperatures.

scholarly journals Chemoselective Ring-Opening Polymerization of Bio-Renewable α-Methylene-γ-Butyrolactone via an Organophosphazene/urea Binary Synergistic Catalytic System Toward a Sustainable Polyester

2020 ◽  
Author(s):  
Yong Shen ◽  
Wei Xiong ◽  
YongZheng Li ◽  
ZhiChao Zhao ◽  
Hua Lu ◽  
...  
Keyword(s):  
Double Bond ◽  
Catalytic System ◽  
Low Temperatures ◽  
Ring Opening ◽  
Theoretical Calculations ◽  
Unsaturated Polyester ◽  
Ring Opening Polymerization ◽  
Membered Ring ◽  
Exocyclic Double Bond ◽  
Binary Catalyst

Despite the great potential of bio-renewable a-methylene-<a></a><a></a><a>g-butyrolactone</a> (MBL) to produce functional recyclable polyester, the ring-opening polymerization (ROP) of MBL remains as a challenge due to the competing polymerization of the highly reactive exocyclic double bond and the low strained five membered ring. In this contribution, we present the first organocatalytic chemoselective ROP of MBL to exclusively produce recyclable unsaturated polyester by utilizing a phosphazene base/urea binary catalyst. We show that delicate chemoselectivity can be realized by controlling the temperature and using selected urea catalysts. Experimental and theoretical calculations provide mechanistic insights and indicate that the kinetically controlled ROP pathway is favored by using urea with stronger acidity at low temperatures.

Chemistry of meso-Dimethylaminopropenyl- porphyrins and -bisporphyrins: the Synthesis of Australochlorin, a Benzochlorin Isomer.

1997 ◽  
Vol 50 (5) ◽  
pp. 487 ◽  
Author(s):  
Dmitry V. Yashunsky ◽  
Gelii V. Ponomarev ◽  
A. S. Moskovkin ◽  
Dennis P. Arnold
Keyword(s):  
Acetic Acid ◽  
Double Bond ◽  
Trifluoroacetic Acid ◽  
Membered Ring ◽  
Macrocyclic Complexes ◽  
Exocyclic Double Bond ◽  
Derivatives Of

The nickel(II) complex of meso-dimethylaminoprop-1-enyloctaethylporphyrin (2c) was converted by quaternization and thermolysis into a pair of novel isomeric macrocyclic complexes (3) and (4). These have a fused six-membered ring, and an exocyclic double bond on the neighbouring β-position, and have been named ‘australochlorins’. Heating these compounds in acetic acid leads to the known nickel(II) octaethylbenzochlorin (1) and a novel β-(1-acetoxyethyl)benzochlorin (5). Trifluoroacetic acid promotes the regioselective formation of benzochlorin/porphyrin species from the mononickel(II) complexes of the acrolein derivatives of bis(octaethylporphyrinyl)ethane and trans-ethene.

scholarly journals Stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene: a general intramolecular Diels–Alder approach to tricyclic sesquiterpenes

1985 ◽  
Vol 63 (4) ◽  
pp. 993-995 ◽  
Author(s):  
Kazimierz Antczak ◽  
John F. Kingston ◽  
Alex G. Fallis
Keyword(s):  
Double Bond ◽  
Methyl Ester ◽  
Total Synthesis ◽  
Ring System ◽  
Diels Alder ◽  
Exocyclic Double Bond ◽  
Total Syntheses ◽  
Methyl Group ◽  
Secondary Hydroxyl ◽  
Selective Hydrogenolysis

Stereoselective total synthesis of (±)-sinularene and (±)-5-epi-sinularene are described. The sequence employs a "blocked" cyclopentadiene in which the cyclopropane unit also serves as a latent methyl group. Thus intramolecular [4 + 2] cycloaddition of the substituted methyl spiro[2.4]hepta-4,6-dien-1-yl)-2-pentenoate 11 affords 5-benzyloxy-6-isopropyl-8-carbomethoxytetracyclo[5.4.01,7.02,4.02,9]undec-10-ene (12) which after selective hydrogenolysis generates the tricyclo[4.4.01,6.02,8]decane (sinularene) ring system. Removal of the secondary hydroxyl function (Ph3P/CCl4/CH3CN; H2/Pd/C), reduction of the methyl ester (LiAlH4), and introduction of the exocyclic double bond (acetate pyrolysis, 550 °C) completes the synthesis of (±)-sinularene in 14 steps from cyclopentadiene. A parallel series of reactions employing the isopropyl epimer of 12 affords (±)-5-epi-sinularene.

Formation of Dihydroaza-azulanones Possessing Spirocyclic Moieties: [8+2] Type Cycloaddition Reactions of Iminotropones to an Exocyclic Double Bond of 8-Oxoheptafulvene

Heterocycles ◽  
1995 ◽  
Vol 41 (10) ◽  
pp. 2181 ◽  
Author(s):  
Katsuhiro Saito ◽  
Yuka Saito ◽  
Masayuki Tomita ◽  
Hiroshi Taniguchi ◽  
Hirofumi Okabayashi
Keyword(s):  
Double Bond ◽  
Exocyclic Double Bond ◽  
Cycloaddition Reactions

Additionen an die Si=N-Doppelbindung – Kristallstruktur eines (SiNCO)-Vierringes / Additions to the Si=N-Double Bond - Crystal Structure of a (SiNCO)-Four Membered Ring

1991 ◽  
Vol 46 (6) ◽  
pp. 709-713 ◽  
Author(s):  
Susanne Vollbrecht ◽  
Uwe Klingebiel ◽  
Dieter Schmidt-Bäse
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Single Crystals ◽  
Membered Ring ◽  
Thermal Cleavage

In the reaction with benzophenone and phenylaldehyde lithiated aminofluorosilanes behave like iminosilanes. Four membered rings are formed in (2+2) cycloadditions. The oxaazasilacyclobutane ((CMe3)2Si—NCMe3—C6H5CH—O—) was purified by destillation. Single crystals were obtained by recrystallization from hexane. The thermal cleavage of the (SiNCO)-rings leads to carboimines and cyclosiloxanes. The lithium derivate of di-tert-butylfluorosilyl-2.6-diisopropylphenylamine reacts with 2-methyl-propenal-2 in two competing ways. In a (2+4) cycloaddition an 1-oxa-3-aza-2-sila-5-cyclohexene is formed, and in a (2+2) cycloaddition 2-methyl-2-propenyl-N-(2.6-diisopropylphenyl)imine is generated via an (SiNCO)-ring intermediate.

Structurally original oxathioethers macrocycles containing an exocyclic double-bond: synthesis, characterization, reactivity, and coordination

Tetrahedron ◽  
2014 ◽  
Vol 70 (35) ◽  
pp. 5650-5658 ◽  
Author(s):  
Guillaume Carel ◽  
Alina Saponar ◽  
Nathalie Saffon ◽  
Marc Vedrenne ◽  
Stéphane Massou ◽  
...  
Keyword(s):  
Double Bond ◽  
Exocyclic Double Bond
Sign in / Sign up

Export Citation Format

Share Document