Thujopsene rearrangements. Ring system via ring contraction

1972 ◽  
Vol 37 (2) ◽  
pp. 251-259 ◽  
Author(s):  
W. G. Dauben ◽  
E. I. Aoyagi
Keyword(s):  
Ring System ◽  
Ring Contraction

Untersuchungen zur Ringkontraktion am 1,4-Dithia-2,6-diaza-3,5-diborinan-System/ Studies on Ring Contraction of the l,4-Dithia-2,6-diaza-3,5-diborinane System

1988 ◽  
Vol 43 (8) ◽  
pp. 959-962 ◽  
Author(s):  
Carl Habben ◽  
Anton Meiler ◽  
Stefan Pusch
Keyword(s):  
Mass Spectra ◽  
Ring System ◽  
Membered Ring ◽  
Ring Contraction ◽  
C Nmr

AbstractThe 1,4-dithia-2,6-diaza-3,5-diborinanes 1a-d react with elemental sodium with formation of the 1,3-diaza-2,4-diboretidines 2a-d. By use of more sodium in case of 1 d or 3,5-bis(diethylamino)- 2-cyclohexyl-6-trimethylsilyldiborinane, the 1,3-thiaza-2,4-diboretidines 3 were formed. 3.5-Dimethyl-2,6-bis(trimethylsilyl)-1,4-dithia-2,6-diaza-3,5-diborinane gives the borazine 4, The reaction of di-t-butyl-sulfurdiimide with 2,6-di-t-butyl-3,5-dimethyl-1,4-dithia-2,6-diaza-3,5-diborinane leads by ring contraction to the four-membered ring system 5. 1H, 11B, 13C NMR and mass spectra are reported and discussed.

Cyclophanes. VI. The synthesis of [2,2](3,3')biphenylparacyclophanedienes

1976 ◽  
Vol 29 (6) ◽  
pp. 1267 ◽  
Author(s):  
PJ Jessup ◽  
JA Reiss
Keyword(s):  
Ring Opening ◽  
Ring System ◽  
Ring Contraction ◽  
Stevens Rearrangement ◽  
Ring Opening Reaction ◽  
Disubstituted Benzene ◽  
Contraction Procedure

The preparations of [2,2](3,3')biphenylparacyclophane-1,9-dine (19) and a dimethyl derivative (20) synthesized by a ring-contraction procedure of the corresponding dithiacyclophanes (11) and (12) are reported. Both dienes (19) and (20) photocyclized under oxidative conditions to the benzo[ghi]- perylenes (21) and (22). Difficulties associated with the Stevens rearrangement in cyclophanes containing a para-disubstituted benzene moiety have been rationalized in terms of a competing ring- opening reaction. Several other reactions of the biphenylparacylophane ring system are reported, and the stereochemistry of the macrocycle is discussed.

Studies on the synthesis of the decahydro-as-indacene ring system of (-)-spinosyn A via transannular Diels-Alder reactions of substituted (E,E,E)-cyclododeca-1,6,8-trienes

2000 ◽  
Vol 78 (6) ◽  
pp. 757-771 ◽  
Author(s):  
Scott A Frank ◽  
Andrea B Works ◽  
William R Roush
Keyword(s):  
Transition State ◽  
Alder Reaction ◽  
Ring System ◽  
Diels Alder ◽  
Tandem Reactions ◽  
Ring Contraction ◽  
Diels Alder Reaction ◽  
Key Features ◽  
Stereoselective Syntheses

Stereoselective syntheses of decahydro-as-indacenes 31 and 54 are reported. The key features of our syntheses of 31 and 54 are the tandem Ireland-Claisen ring contraction of lactones 29 and 38 followed by the transannular Diels-Alder cyclization of cyclododecatrienes 30 and 35. Transition state modeling of both the transannular Diels-Alder reaction and the Ireland-Claisen ring contraction using PCModel is also described.Key words: transannular Diels-Alder reactions, tandem reactions, Claisen ring contraction, Spinosyn A, synthetic study.

Cyclophanes. IV. Synthetic approaches to cyclophane dienes. The preparation of [2,2](2,7)Naphthalenophane-1,11-diene

1976 ◽  
Vol 29 (1) ◽  
pp. 163 ◽  
Author(s):  
JR Davy ◽  
JA Reiss
Keyword(s):  
Ring System ◽  
Ring Contraction ◽  
Stevens Rearrangement ◽  
Elimination Procedure ◽  
Synthetic Approaches ◽  
Hofmann Elimination

The synthesis of [2,2](2,7)naphthalenophane-1,ll-diene (2a) from 2,13-dithia[3,3](2,7)naphthalenophane (4) by means of a Stevens rearrangement ring contraction and a Hofmann elimination procedure is described. The diene was found to undergo an efficient oxidative photochemical cyclization to coronene. Several other reactions of the naphthalenophane ring system are described, and the stereochemistry of the macrocycle is discussed.

scholarly journals Reaktionen am Cyclotrisilazan-System - Synthese und Molekülstruktur eines 1.3.5.7-Tetraaza-2.4.6.8-tetrasila-bicyclo [4.2.0] octans / Reactions of the Cyclotrisilazane System - Synthesis and Molecular Structure of a 1,3,5,7-Tetraaza-2,4,6,8-tetrasilabicyclo[4,2,0]octane

1980 ◽  
Vol 35 (12) ◽  
pp. 1503-1507 ◽  
Author(s):  
William Clegg ◽  
Uwe Klingebiel ◽  
George M. Sheldrick ◽  
Lutz Skoda ◽  
Norbert Vater
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Structure Determination ◽  
Title Compound ◽  
Ring System ◽  
Molar Ratio ◽  
Compound A ◽  
Ring Contraction ◽  
Fused Ring ◽  
Fused Ring System

1,3-Dilithio-5-trimethylsilyl-2,2,4,4,6,6-hexamethylcyclotrisilazane (1) reacts in a 1:2 molar ratio with difluorodimethyl- or trifluoromethylsilane to give substitution at the lithiated N atoms. The reaction of the bis(fluorodimethylsilyl)-substituted compound with more of 1 produces ring contraction, to form a silyl-bridged tris(cyclodisilazane). In the reaction of the bis(difluoromethylsilyl)-substituted cyclotrisilazane with more of 1, however, the title compound, a fused ring system, is formed. This compound has been characterised by crystal structure determination. The mechanism of its formation is discussed.

Reactions of Fervenulone. An Unprecedented Ring Contraction of a 7-Azapteridine Ring System

1995 ◽  
Vol 60 (21) ◽  
pp. 7063-7065 ◽  
Author(s):  
Mukund M. Mehrotra ◽  
Daniel D. Sternbach ◽  
Randy D. Rutkowske ◽  
Paul L. Feldman
Keyword(s):  
Ring System ◽  
Ring Contraction

Bicyclo[2.2.2]octane-2-spirocyclohexanes, Part 3. Synthesis and Reactions of Mono- and Dibromospirodiisophoranes

1992 ◽  
Vol 47 (1) ◽  
pp. 126-138 ◽  
Author(s):  
Frederick Kurzer ◽  
Zakir Kapadia
Keyword(s):  
Nmr Spectra ◽  
Ring System ◽  
Lithium Aluminium Hydride ◽  
Ring Contraction ◽  
Lithium Aluminium ◽  
The Individual ◽  
C Nmr

Halogenation by the appropriate amounts of bromine or N-bromosuccinimide converts spirodiisophora-3',6-dione successively into the 4'-ax-mono- and 2',4'-diax-dibromo-3',6-dione. The latter is reduced by lithium aluminium hydride to the corresponding 6,3'-ketol. with retention of one or both bromo-substituents, depending on conditions. The bromoketones undergo the Favorski ring-contraction under the influence of alkalis to compounds of the bicyclo[2.2.2]octane-2-spirocyclopentane ring-system . The 13C NMR spectra of the individual products are assigned and correlated with their structures.

scholarly journals Mechanistic Investigation of a Novel Medium-Sized Ring Rearrangement

Synlett ◽  
2017 ◽  
Vol 29 (05) ◽  
pp. 589-592
Author(s):  
Alan Jones ◽  
Aneesa Al-Ani
Keyword(s):  
Ring System ◽  
Supporting Evidence ◽  
Dominant Mechanism ◽  
Ring Contraction ◽  
Mechanistic Investigation ◽  
First Time

The dominant mechanism operating in a recently disclosed ring contraction is revealed for the first time. New insight and supporting evidence into a classic ring-contraction strategy within a rigidified larger ring system are provided.

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