ChemInform Abstract: Total Syntheses of CP-225,917 and CP-263,114: Creation of a Matrix Structure by Sequential Aldol Condensation and Intramolecular Heck Ring Closure.

ChemInform ◽  
2010 ◽  
Vol 29 (49) ◽  
pp. no-no
Author(s):  
O. KWON ◽  
D.-S. SU ◽  
D. MENG ◽  
W. DENG ◽  
D. C. D'AMICO ◽  
...  
Keyword(s):  
Aldol Condensation ◽  
Ring Closure ◽  
Matrix Structure ◽  
Total Syntheses

Annulations leading to diene systems. Total syntheses of the dolastane-type diterpenoids (±)-(5S,12R,14S)-dolasta-1(15),7,9-trien-14-ol and (±)-amijitrienol

1992 ◽  
Vol 70 (4) ◽  
pp. 1204-1220 ◽  
Author(s):  
Edward Piers ◽  
Richard W. Friesen
Keyword(s):  
Aldol Condensation ◽  
Ring Closure ◽  
Starting Material ◽  
Target Compound ◽  
One Pot ◽  
Stereoselective Reduction ◽  
Total Syntheses ◽  
Reductive Transformation ◽  
The One ◽  
Key Steps

Alkylation of the substituted cycloalkanones 14a–d and 30 with (Z)-1-bromo-4-methyl-3-trimethylstannyl-2-pentene (13) produced compounds 15a–d and 33, which were readily converted into the corresponding enol trifluoromethane-sulfonates (triflates) 16a–d and 34. Intramolecular Pd(O)-catalyzed coupling of the vinylstannane and enol triflate functions in 16a–d and 34 provided the dienes 17a–d and 35. The annulation product 35 served as a suitable starting material for the total syntheses of the dolastane diterpenoids (±)-(5S,12R,14S)-dolasta-1(15),7,9-trien-14-ol (2) and (±)-amijitrienol (3). The key steps of the synthesis of (±)-2 involved the stereoselective methylation of the ketone 44 (readily derived from 35) to provide 46 and the Barbier type ring closure of 47 to provide the target compound. For the synthesis of (±)-3, the notable conversions included the reductive transformation of the diene 35 into the alkene 53, the aldol condensation of the ketone 54 with 4-trimethylstannyl-4-pentenal (55), the chemo- and stereoselective reduction of the dione 58, and the one-pot conversion of the keto vinylstannane 63 into the triene 65, via the intermediate 64.

Catalyst-Free One-Pot Synthesis of Novel Heteroarylamine Substituted Furo[3,2-c]coumarins

Synlett ◽  
2018 ◽  
Vol 29 (12) ◽  
pp. 1589-1592 ◽  
Author(s):  
Abolfazl Olyaei ◽  
Mahnaz Saraei ◽  
Reyhaneh Khoeiniha
Keyword(s):  
Michael Addition ◽  
Aldol Condensation ◽  
Ring Closure ◽  
Dehydration Reaction ◽  
One Pot ◽  
Catalyst Free ◽  
One Pot Synthesis ◽  
Tandem Process ◽  
First Time

A high-yielding cyclocondensation of 4-hydroxycoumarin, phenylglyoxal monohydrate, and heteroarylamines proceeds without catalysis, which gives novel functionalized furo[3,2-c]coumarins and heteroarylamino alkylation of coumarin products in acetonitrile under reflux, is reported for the first time. This tandem process involves sequentially an aldol condensation, Michael addition, a ring closure, and dehydration reaction.

Total syntheses of (±)-penicibilaenes A and B via intramolecular aldol condensation

2021 ◽  
Author(s):  
Rintaro Matsuo ◽  
Ayumu Watanabe ◽  
Shogo Kamo ◽  
Akinobu Matsuzawa ◽  
Kazuyuki Sugita
Keyword(s):  
Aldol Condensation ◽  
Total Syntheses

Concise total syntheses of penicibilaenes A and B were achieved via intramolecular aldol condensation and other key reactions.

The Williams Synthesis of (–)-Khayasin

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Natural Product ◽  
Claisen Rearrangement ◽  
Aldol Condensation ◽  
Secondary Alcohol ◽  
Alcohol Exposure ◽  
Leaf Beetle ◽  
Allylic Alcohol ◽  
Total Syntheses ◽  
Asymmetric Transformation ◽  
The University

The tetranortriterpenoid (–)-khayasin 3 recently emerged as a potent and selective insecticide against the Coconut leaf beetle Brontispa longissima. In considering a synthetic route to 3, Craig M. Williams of the University of Queensland envisioned (J. Org. Chem. 2012, 77, 8913) the convergent preparation of the allyl vinyl ether 1 and subsequent Claisen rearrangement to the enone 2. To pursue this strategy, the ketone 8 and the allylic alcohol 15 had to be prepared in enantiomerically pure form. To this end, the DIP-Cl-derived enolate of the ketone 7 was added to the aldehyde 6 to give a secondary alcohol, exposure of which to KH led to the enone 8 in high ee. Methyl triflate converted the enone into the enol ether 9. The α-pinene used in the preparation of DIP-Cl was 83% ee. The authors have optimized (Adv. Synth. Catal. 2009, 351, 1148) the Morita-Baylis-Hillman addition of cyclohexenone 10 to formaldehyde to give, after silylation, the enone 11. Methylation followed by DIP-mediated aldol condensation with 13 led to the alcohol 14. Exposure of the derived acetate to lithium diisopropylamide induced cyclization and dehydration. Deprotection completed the preparation (Tetrahedron 2006, 62, 7355) of 15. Fortunately, the enantiomers of 15 could be separated chromatographically. Material having >99% ee was taken onto the next step. Warming of 9 and 15 in the presence of acid delivered the coupled ketone 2 accompanied by the ether 1. Further heating of 1 converted it (Chem. Commun. 2011, 47, 2258) to 2. To form the last ring, the enone 2 was epoxidized to give 16. The reduction of 16 with aluminum amalgam gave preparatively useful amounts of 17. Esterification completed the synthesis of 3. Most total syntheses yield only the target natural product. In this biomimetic project, intermediates 15, 2, and 17 were themselves natural products, and oxidation of 17 delivered an additional natural product, 18. The preparation of 14 and of 8 underscores the importance of the asymmetric transformation of prochiral starting materials, cyclic and acyclic. Although DIP-Cl is used in stoichiometric amounts in both cases, it is not expensive. The preparation of 8, in particular, offers a potentially general approach to high ee-substituted cyclohexenones.

Formation of Persistent Slip Band in Fatigued Copper Single Crystals

1982 ◽  
Vol 40 ◽  
pp. 470-471
Author(s):  
N. Y. Jin
Keyword(s):  
Volume Fraction ◽  
Fatigue Cracks ◽  
Wall Structure ◽  
Matrix Structure ◽  
Dislocation Dipole ◽  
Slip Bands ◽  
Persistent Slip Bands ◽  
The Matrix ◽  
Hard Shell ◽  
Copper Single Crystals

Localised plastic deformation in Persistent Slip Bands(PSBs) is a characteristic feature of fatigue in many materials. The dislocation structure in the PSBs contains regularly spaced dislocation dipole walls occupying a volume fraction of around 10%. The remainder of the specimen, the inactive "matrix", contains dislocation veins at a volume fraction of 50% or more. Walls and veins are both separated by regions in which the dislocation density is lower by some orders of magnitude. Since the PSBs offer favorable sites for the initiation of fatigue cracks, the formation of the PSB wall structure is of great interest. Winter has proposed that PSBs form as the result of a transformation of the matrix structure to a regular wall structure, and that the instability occurs among the broad dipoles near the center of a vein rather than in the hard shell surounding the vein as argued by Kulmann-Wilsdorf.

Characterization of Chemical Impurities in Glutaraldehyde

1975 ◽  
Vol 33 ◽  
pp. 620-621
Author(s):  
B. J. Grenon ◽  
A. J. Tousimis
Keyword(s):  
Glutaric Acid ◽  
Spectroscopic Analysis ◽  
Aldol Condensation ◽  
Condensation Product ◽  
Amorphous Solid ◽  
Water Soluble ◽  
Impurity Component ◽  
Chemical Impurities ◽  
Soluble Liquid

Ever since the introduction of glutaraldehyde as a fixative in electron microscopy of biological specimens, the identification of impurities and consequently their effects on biologic ultrastructure have been under investigation. Several reports postulate that the impurities of glutaraldehyde, used as a fixative, are glutaric acid, glutaraldehyde polymer, acrolein and glutaraldoxime.Analysis of commercially available biological or technical grade glutaraldehyde revealed two major impurity components, none of which has been reported. The first compound is a colorless, water-soluble liquid with a boiling point of 42°C at 16 mm. Utilizing Nuclear Magnetic Resonance (NMR) spectroscopic analysis, this compound has been identified to be — dihydro-2-ethoxy 2H-pyran. This impurity component of the glutaraldehyde biological or technical grades has an UV absorption peak at 235nm. The second compound is a white amorphous solid which is insoluble in water and has a melting point of 80-82°C. Initial chemical analysis indicates that this compound is an aldol condensation product(s) of glutaraldehyde.

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