Claisen Ring Expansion Approach toward the CDEF Ring System of Lancifodilactone G

Heterocycles ◽  
2009 ◽  
Vol 79 (1) ◽  
pp. 299 ◽  
Author(s):  
Leo A. Paquette ◽  
Kwong Wah Lai
Keyword(s):  
Ring Expansion ◽  
Ring System

Synthetic studies related to mycobactins. III. Approaches to the synthesis of the cobactin ring system

1972 ◽  
Vol 25 (11) ◽  
pp. 2429 ◽  
Author(s):  
DSC Black ◽  
RFC Brown ◽  
AM Wade
Keyword(s):  
Primary Amine ◽  
Ring Expansion ◽  
Hydroxamic Acids ◽  
Ring System ◽  
Ethyl Benzoate ◽  
Yield Reduction ◽  
Similar Reaction ◽  
Oxidation Reactions ◽  
Cyclic Hydroxamic Acids ◽  
Synthetic Studies

The synthesis of several seven-membered cyclic hydroxamic acids has been carried out in low yield. Reduction of diethyl 2-hydroxyiminoheptane-l,7-dioate afforded ethyl 1-hydroxy-7-oxohexahydroazepine-2-carboxylate, together with related acyclic products. The cobactin precursor 3-bromo-1-hydroxyhexahydro-azepin-2-one was obtained by the ring expansion of 2-bromocyclohexanone with benzenesulphonohydroxamic acid and also by the peracid oxidation of 6-bromo-7-ethoxy-3,4,5,6-tetrahydro-2H-azepine. The methyl and cinnamyl imidates of hexanolactam were oxidized by peracid to 1-hydroxyhexahydroazepin-2-one, in addition to the related imino- and nitroso-hexanoic esters. In a similar reaction, 1-hydroxypiperidin-2-one was obtained from 2-methoxy-3,4,5,6-tetrahydropyridine. During the course of these oxidation reactions, the intermediate oxaziridines 7-methoxy-8-oxa-1-azabicyclo[5,1,0]octane and 6-bromo-7-ethoxy-8-oxa-1-azabicyclo[5,1,0]octane were isolated and identified. The peraoid oxidation of ethyl N-cyclohexylbenzimidate yielded cyclohexylhydroxylamine and ethyl benzoate in reasonable yields. This reaction suggests a useful method for the conversion of a primary amine into the related hydroxylamine.

The Reaction of 2-Hydro-2-oxo-5,6-benzo-l,3,2λ4-dioxaphosphorin-4-one with Imines and Carbonyl Compounds; Unusual Formation and First X-Ray Crystal Structure Determination of a Benzodioxaphosphepinone Ring System

1996 ◽  
Vol 51 (10) ◽  
pp. 1501-1510 ◽  
Author(s):  
Thomas Kaukorat ◽  
Ion Neda ◽  
Holger Thönnessen ◽  
Peter G. Jones ◽  
Reinhard Schmutzler
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Structure Determination ◽  
Ring Expansion ◽  
Ring System ◽  
Crystal Structure Determination ◽  
Insertion Reaction ◽  
X Ray ◽  
Ir Spectroscopic

On treatment of 2-hydro-2-oxo-5,6-benzo-1,3,2λ4-dioxaphosphorin-4-one (1) with the inline trimers trim ethyl- and tribenzyltriazine and the (monomeric) methylene-tert-butylimine, an insertion reaction of the imine molecule into the P-H bond of 1 took place, forming com pounds 2 -4 . Similar results were obtained when 1 was allowed to react with aldimines, asymmetric at carbon, leading to 5-7 . The diastereotopic properties of 5 - 7 were observed by 1H NMR spectroscopy. NMR and IR spectroscopic investigations on 5 - 7 indicated > C = O···H-N < interactions. Upon reaction of 1 with hexafluoroacetone, trifluoroacetophenone or phenyltrifluoromethylketimine, the derivatives 8 -1 0 , involving a P-O-C fragment, were obtained. The formation of the isomeric “alcohol form ”, bearing a P-C-OH fragment, could not be proved. In the reaction of 1 with various o-quinones. one of the oxygen atom s of the quinone was found to be bonded to phosphorus, whereas the hydrogen atom was found to migrate to the second oxygen atom . Upon reaction of 1 with chloral, an unusual ring expansion took place with formation of the benzodioxaphosphepinone (14). The reaction of 1 with other aldehydes could not be realized. In the reaction of 14 with triethylamine, the ammonium salt 15 was formed. For the first time, an X-ray crystal structure determination of a dioxaphosphepinone ring system was conducted; in 15 the seven-membered ring displays a pseudo tub conformation.

scholarly journals Synthesis of a New Type of Trans-Decalin Vitamin D Analogue through a Dyotropic Ring Expansion

2021 ◽  
Vol 2021 ◽  
pp. 1-5
Author(s):  
Hugo Santalla ◽  
Uxía Gómez-Bouzó ◽  
Irene Sánchez-Sanz ◽  
Yagamare Fall
Keyword(s):  
Vitamin D ◽  
Research Group ◽  
Ring Expansion ◽  
Ring System ◽  
Side Chain ◽  
Sulphur Atom ◽  
Mild Conditions ◽  
New Type ◽  
Vitamin D Analogue

A new vitamin D analogue with a trans-fused decalin as the CD-ring system and containing a sulphur atom in the side chain has been synthesized in our research group. The obtention of this analogue is based on a recently discovered transformation of hydrindane cores into decalins through a dyotropic ring expansion in very mild conditions.

Synthesis and Applications of Cyclopropanones and their Equivalents as Three-Carbon Building Blocks in Organic Synthesis

Synthesis ◽  
2021 ◽  
Author(s):  
Yujin Jang ◽  
Roger Machin-Rivera ◽  
Vincent Lindsay
Keyword(s):  
Organic Synthesis ◽  
Ring Opening ◽  
Building Blocks ◽  
Ring Expansion ◽  
Ring System ◽  
Small Ring ◽  
Future Directions ◽  
Highly Strained ◽  
And Storage

Cyclopropanone derivatives constitute highly strained cycloalkanones with promising applications as three-carbon building blocks in organic synthesis. Due to the presence of a ketone in such a small ring system, all C–C bonds and the carbonyl group are considered to be labile in suitable conditions, leading to a wide variety of synthetic disconnections, including nucleophilic addition, ring expansion, ring-opening and (formal) cycloaddition. Despite their synthetic potential, the widespread adoption of cyclopropanones as substrates has been considerably hampered by the difficulties associated with the preparation and storage of such unstable compounds, prompting the development of cyclopropanone surrogates that can equilibrate to parent ketone in situ via elimination. This review summarizes the syntheses and applications of cyclopropanone derivatives and their equivalents, and offers a perspective of the state of the field as well as its expected future directions.

N,N-Dialkyl-N′-Chlorosulfonyl Chloroformamidines in Heterocyclic Synthesis. Part XII. Synthesis and Reactivity of the Pyrazolo[3,4-e][1,2,4]thiadiazine Ring System

2015 ◽  
Vol 68 (9) ◽  
pp. 1455 ◽  
Author(s):  
Rebecca E. Norman ◽  
Michael V. Perkins ◽  
Andris J. Liepa ◽  
Craig L. Francis
Keyword(s):  
Pyrazole Ring ◽  
Ring Expansion ◽  
Ring System ◽  
Heterocyclic Synthesis ◽  
Ethyl Bromoacetate

N,N-Dialkyl-N′-chlorosulfonyl chloroformamidines 1 reacted regioselectively with 1-substituted 5-aminopyrazoles 2 via a 1,3-CCN dinucleophilic substitution to afford pyrazolo[3,4-e][1,2,4]thiadiazines 3 as the sole isolated products. Compounds 3, representatives of a very rare ring system, were shown to possess three nucleophilic sites at N2, N4, and N6. Methylation occurred at all three sites. Alkylation with benzylic halides occurred preferentially at N2, but some also occurred at N4, and at C7a. Alkylation with ethyl bromoacetate occurred at both N4 and N6, but the latter derivatives underwent a pyrazole ring expansion to afford pyrimido[4,5-e][1,2,4]thiadiazine derivatives. Compounds 3 were unreactive towards various acylating agents.

A Pauson−Khand and Ring-Expansion Approach to the Aquariane Ring System

2006 ◽  
Vol 8 (15) ◽  
pp. 3195-3198 ◽  
Author(s):  
Paul D. Thornton ◽  
D. Jean Burnell
Keyword(s):  
Ring Expansion ◽  
Ring System

scholarly journals A Biomimetic Synthetic Approach to the Frondosins

2016 ◽  
Vol 69 (12) ◽  
pp. 1420 ◽  
Author(s):  
Kevin K. W. Kuan ◽  
Aylin M. C. Hirschvogel ◽  
Jonathan H. George
Keyword(s):  
Marine Sponge ◽  
Ring Expansion ◽  
Cascade Reaction ◽  
Ring System ◽  
Biomimetic Synthesis ◽  
Synthetic Approach ◽  
Compelling Evidence

The frondosins are a family of five marine sponge-derived meroterpenoids. We propose that the 6–7 ring system common to each of the frondosins is biosynthesized via ring expansion of a 6–6 ring system. Compelling evidence in favour of this proposal was obtained in the form of a biomimetic synthesis of the frondosin 6–7 ring system, which features a highly stereo- and regio-selective ring expansion cascade reaction as the key step.

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