scholarly journals Synthesis of Benzo[b]fluorenone Nuclei of Stealthins

2009 ◽  
Vol 2009 ◽  
pp. 1-5
Author(s):  
Sujit Kumar Ghorai ◽  
Saroj Ranjan De ◽  
Raju Karmakar ◽  
Nirmal Kumar Hazra ◽  
Dipakranjan Mal
Keyword(s):  
Aldol Condensation ◽  
The Other ◽  
Ene Reaction ◽  
Michael Adduct ◽  
Nef Reaction

Two routes, one based on a Michael-initiated aldol condensation and the other on an intramoleculer carbonyl-ene reaction, have been found to be feasible for an entry to benzo[b]fluorenones. Reaction of 4,9-dimethoxybenz[f]indenone with nitromethane in the presence of DBU gave the corresponding Michael adduct, which afforded 2-methyl-5,10-dimethoxybenzo[b]fluorenone on reaction with methacrolein under a variety of basic conditions. Similarly, 2-methallyl-4,9-dimethoxybenz[f]indenone reacted with nitromethane to give the corresponding Michael adduct, Nef reaction of which furnished 3-formyl-2-methyl-4,9-dimethoxybenz[f]indanone. This underwent ene-cyclization under the influence of SnCl4. 5H2O, and yielded 2-methyl-5,10-dimethoxybenzo[b]fluorenone.

The Fürstner Synthesis of Amphidinolide F

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Amino Alcohol ◽  
Aldol Condensation ◽  
Free Acid ◽  
The Other ◽  
Unsaturated Ester ◽  
Alkyne Metathesis ◽  
Max Planck ◽  
Ring Closing Metathesis ◽  
Enantiomerically Pure ◽  
Metathesis Catalyst

The amphidinolides, having zero, one, or (as exemplified by amphidinolide F 3) two tetrahydrofuran rings, have shown interesting antineoplastic activity. It is a tribute to his development of robust Mo catalysts for alkyne metathesis that Alois Fürstner of the Max-Planck-Institut für Kohlenforschung Mülheim could with confidence design (Angew. Chem. Int. Ed. 2013, 52, 9534) a route to 3 that relied on the ring-closing metathesis of 1 to 2 very late in the synthesis. Three components were prepared for the assembly of 1. Julia had already reported (J. Organomet. Chem. 1989, 379, 201) the preparation of the E bromodiene 5 from the sulfone 4. The alcohol 7 was available by the opening of the enantiomerically-pure epoxide 6 with propynyl lithium, followed by oxidation following the Pagenkopf pro­tocol. Amino alcohol-directed addition of the organozinc derived from 5 to the alde­hyde from oxidation of 7 completed the assembly of 8. Addition of the enantiomer 10 of the Marshall butynyl reagent to 9 followed by protection, oxidation to 11, and addition of, conveniently, the other Marshall enan­tiomer 12 led to the protected diol 13. Silylcupration–methylation of the free alkyne set the stage for selective desilylation and methylation of the other alkyne. Iodination then completed the trisubstituted alkene of 14. Methylation of the crystalline lactone 15, readily prepared from D-glutamic acid, led to a mixture of diastereomers. Deprotonation of that product followed by an aque­ous quench delivered 16. Reduction followed by reaction with the phosphorane 17 gave the unsaturated ester, that cyclized with TBAF to the crystalline 18. The last ste­reogenic center of 22 was established by proline-mediated aldol condensation of the aldehyde 19 with the ketone 20. To assemble the three fragments, the ketone of 21 was converted to the enol triflate and thence to the alkenyl stannane. Saponification gave the free acid 22, that was acti­vated, then esterified with the alcohol 18. Coupling of the stannane with the iodide 14 followed by removal of the TES group led to the desired diyne 1. It is noteworthy that the Mo metathesis catalyst is stable enough to tolerate the free alcohol of 1 in the cyclization to 2.

General and practical approach to the syntheses of linear homoallylic alcohols

2005 ◽  
Vol 77 (7) ◽  
pp. 1199-1206 ◽  
Author(s):  
Hin-Soon Cheng ◽  
Teck-Peng Loh
Keyword(s):  
Optical Purity ◽  
The Other ◽  
New Method ◽  
Practical Approach ◽  
Mechanistic Studies ◽  
Ene Reaction ◽  
Homoallylic Alcohols ◽  
Other Hand ◽  
High Optical Purity ◽  
Judicious Choice

We have demonstrated that metal-mediated allylation of aldehydes can afford γ-homoallylic alcohols or α-linear homoallylic alcohols by judicious choice of the solvents. A new mechanism has been proposed to account for this new α-selective metal-mediated allylation reaction. On the other hand, the metal-mediated prenylation under the same conditions to obtain α-prenyl alcohols was unsuccessful. Detailed mechanistic studies have resulted in the discovery of a new method to obtain compounds with diverse structures via an oxonium-ene cyclization. Suppressing the oxonium-ene reaction during the reaction has resulted in the formation of α-prenyl alcohols. A highly enantioselective process to obtain α-prenyl product in high optical purity has also been accomplished.

Carbocyclic Ring Construction: The Nicolaou Synthesis of Myceliothermophin E

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Claisen Rearrangement ◽  
Aldol Condensation ◽  
Crop Protection ◽  
Cope Rearrangement ◽  
Columbia University ◽  
Tetramic Acid ◽  
Ene Reaction ◽  
Ru Catalyst ◽  
Equilibrium Process ◽  
The University

Nan Zheng of the University of Arkansas developed (Adv. Synth. Catal. 2014, 356, 2831) a Ru catalyst for the addition of an amino cyclopropane 1 to an alkyne 2 to give 3. The reaction proceeded with high regiocontrol, but only modest stereocontrol. Alain De Mesmaeker of Syngenta Crop Protection, Switzerland found (Tetrahedron Lett. 2014, 55, 6577) that the β,γ-unsaturated amide 4 worked particularly well as a precursor to the keteniminium that cyclized to give, after hydrolysis, the cyclobuta­none 5. Baeyer–Villiger oxidation of 5 led to 5-deoxystrigol 6. David Tymann and Martin Hiersemann of the Technische Universität Dortmund have been exploring (Org. Lett. 2014, 16, 4062; Synthesis 2014, 46, 3110) the intra­molecular carbonyl ene reaction as a tool for the assembly of highly substituted cyclopentanes, as in the conversion of 7 to 8. On oxidation, 8 was readily carried on to the alkene 9. James L. Leighton of Columbia University conceived (J. Am. Chem. Soc. 2014, 136, 9878) the cascade transformation of 10 to 12. Deprotonation/silylation set the stage for Claisen rearrangement to give 11. The subsequent Cope rearrangement is an equilibrium process, driven by the ring strain of 11. K. C. Nicolaou of Rice University described (Angew. Chem. Int. Ed. 2014, 53, 10970) the total synthesis of the cytotoxic tetramic acid derivative myceliothermo­phin E 15. A key step in the synthesis was the intramolecular Michael addition/ aldol condensation that converted 13 to 14.

Role of Different Feedstocks on the Butanol Production Through Microbial and Catalytic Routes

2017 ◽  
Vol 16 (1) ◽  
Author(s):  
Shalini Biswas ◽  
Richa Katiyar ◽  
B. R. Gurjar ◽  
Vikas Pruthi
Keyword(s):  
Wheat Straw ◽  
Aldol Condensation ◽  
The Other ◽  
Barley Straw ◽  
Butanol Production ◽  
Chemical Route ◽  
Oil Reserves ◽  
Extensive Evaluation ◽  
Acetone Butanol Ethanol

Abstract Among the renewable fuels, butanol has become an attractive, economic and sustainable choice because of cost elevation in petroleum fuel, diminishing the oil reserves and an increase of green house effect. Butanol can be derived from renewable sources by using the natural bio-resources and agro-wastes such as orchard wastes, peanut wastes, wheat straw, barley straw and grasses via Acetone Butanol Ethanol (ABE) process. On the other hand, butanol can be directly formed from chemical route involving catalysts also such as from ethanol through aldol condensation. This review presents extensive evaluation for the production of butanol deploying microbial and catalytic routes.

Alkaloid Synthesis: (+)-Deoxoprosopinine (Krishna), Alkaloid (–)-205B (Micalizio), FR901483 (Huang), (+)-Ibophyllidine (Kwon), (–)-Lycoposerramine-S (Fukuyama), (±)-Crinine (Lautens)

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Aldol Condensation ◽  
Indian Institute ◽  
Chiral Auxiliary ◽  
Full Account ◽  
Ene Reaction ◽  
Alkaloid Synthesis ◽  
Stereogenic Centers ◽  
Sequential Addition ◽  
Vinyl Group ◽  
The University

Palakodety Radha Krishna of the Indian Institute of Chemical Technology observed (Synlett 2012, 2814) high stereocontrol in the addition of allyltrimethylsilane to the cyclic imine derived from 1. The product piperidine 2 was carried onto (+)-deoxoprosopinine 3. Glenn C. Micalizio of Scripps Florida condensed (J. Am. Chem. Soc. 2012, 134, 15237) the amine 4 with 5. The ensuing intramolecular dipolar cycloaddition led to 6, which was carried onto the Dendrobates alkaloid (–)-205B 7. Pei-Qiang Huang of Xiamen University showed (Org. Lett. 2012, 14, 4834) that the quaternary center of 9 could be established with high diastereoselectivity by activation of the lactam 8, then sequential addition of two different Grignard reagents. Subsequent stereoselective intramolecular aldol condensation led to FR901843 10. More recently, Professor Huang, with Hong-Kui Zhang, also of Xiamen University, published (J. Org. Chem. 2013, 78, 455) a full account of this work. In an elegant application of the power of phosphine-catalyzed intermolecular allene cycloaddition, Ohyun Kwon of UCLA added (Chem. Sci. 2012, 3, 2510) 12 to the imine 11 to give 13. The cyclization elegantly set two of the four stereogenic centers of (+)-ibophyllidine 14. Tohru Fukuyama of the University of Tokyo initiated (Angew. Chem. Int. Ed. 2012, 51, 11824) a cascade cyclization between the enone 15 and the chiral auxiliary 16. The product lactam 17 was carried onto (–)-lycoposerramine-S 18. Mark Lautens explored (J. Am. Chem. Soc. 2012, 134, 15572) the utility of the intramolecular aryne ene reaction, as illustrated by the cyclization of 19 to 20. Oxidation cleavage of the vinyl group of 20 followed by an intramolecular carbonyl ene reaction led to (±)-crinine 21.

Claisen rearrangement of allyloxyanthraquinones

1979 ◽  
Vol 57 (24) ◽  
pp. 3304-3307 ◽  
Author(s):  
C. M. Wong ◽  
R. Singh ◽  
K. Singh ◽  
H. Y. P. Lam
Keyword(s):  
Claisen Rearrangement ◽  
Major Product ◽  
The Other ◽  
Ene Reaction ◽  
Unusual Behaviour ◽  
Other Hand

Allyloxyanthraquinones showed unusual behaviour during the Claisen rearrangement. Thus, 1-allyloxyanthraquinone 9 rearranged very readily in the presence of benzylamine while 2-allyloxyanthraquinone 13 refused to do rearrangement even under very drastic conditions. On the other hand, 1,2-diallyloxyanthraquinone rearranged with the loss of the 2-allyloxy group as the result of a retro-ene reaction which has not been previously observed while 1,4-di(2′-chloro-2′-propenyloxy)anthraquinone 18 rearranged to give, as a major product, the unsymmetrically substituted anthraquinone 19 which is useful in the synthesis of anthracycline aglycones.

Stromatoporoids from the Famennian (Devonian) Wabamun Formation, Normandville oilfield, north–central Alberta, Canada

1988 ◽  
Vol 62 (03) ◽  
pp. 411-419 ◽  
Author(s):  
Colin W. Stearn
Keyword(s):  
Patch Reef ◽  
Abundant Species ◽  
The Other ◽  
North Central ◽  
Biotic Crisis

Stromatoporoids are the principal framebuilding organisms in the patch reef that is part of the reservoir of the Normandville field. The reef is 10 m thick and 1.5 km2in area and demonstrates that stromatoporoids retained their ability to build reefal edifices into Famennian time despite the biotic crisis at the close of Frasnian time. The fauna is dominated by labechiids but includes three non-labechiid species. The most abundant species isStylostroma sinense(Dong) butLabechia palliseriStearn is also common. Both these species are highly variable and are described in terms of multiple phases that occur in a single skeleton. The other species described areClathrostromacf.C. jukkenseYavorsky,Gerronostromasp. (a columnar species), andStromatoporasp. The fauna belongs in Famennian/Strunian assemblage 2 as defined by Stearn et al. (1988).

D. The Line Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 207-244
Author(s):  
R. P. Kraft
Keyword(s):  
Variable Stars ◽  
The Other ◽  
Line Spectrum ◽  
Afternoon Session ◽  
Empirical Information ◽  
Pulsating Variable Stars ◽  
Almost Continuous ◽  
Informal Approach

(Ed. note:Encouraged by the success of the more informal approach in Christy's presentation, we tried an even more extreme experiment in this session, I-D. In essence, Kraft held the floor continuously all morning, and for the hour and a half afternoon session, serving as a combined Summary-Introductory speaker and a marathon-moderator of a running discussion on the line spectrum of cepheids. There was almost continuous interruption of his presentation; and most points raised from the floor were followed through in detail, no matter how digressive to the main presentation. This approach turned out to be much too extreme. It is wearing on the speaker, and the other members of the symposium feel more like an audience and less like participants in a dissective discussion. Because Kraft presented a compendious collection of empirical information, and, based on it, an exceedingly novel series of suggestions on the cepheid problem, these defects were probably aggravated by the first and alleviated by the second. I am much indebted to Kraft for working with me on a preliminary editing, to try to delete the side-excursions and to retain coherence about the main points. As usual, however, all responsibility for defects in final editing is wholly my own.)

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

Observing programme for the 24-inch/36-inch Schmidt telescope

1966 ◽  
Vol 24 ◽  
pp. 337
Author(s):  
W. Iwanowska
Keyword(s):  
The Other ◽  
Schmidt Telescope ◽  
Flint Glass

A new 24-inch/36-inch//3 Schmidt telescope, made by C. Zeiss, Jena, has been installed since 30 August 1962, at the N. Copernicus University Observatory in Toruń. It is equipped with two objective prisms, used separately, one of crown the other of flint glass, each of 5° refracting angle, giving dispersions of 560Å/mm and 250Å/ mm respectively.

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