934-02-1Relevant academic research and scientific papers
Hydroboration of 1,1′-bi(cyclopent-1-ene) and 3,3′-biindene: Experimental and theoretical study
Kvicala, Jaroslav,Baszczynski, Ondrej,Krupkova, Alena,Stranska, Denisa
, p. 1611 - 1626 (2006)
Hydroboration of bi(cyclopent-1-ene) (1) or 3,3′-biindene (2) with borane, thexylborane or (-)-isopinocampheylborane afforded, regardless of reaction conditions, meso-isomers of polycyclic 1,4-diols 3a, 4a as the main products. No reaction was observed with 9-BBN. The structure of the major product 4a, as well as of the minor racemic product 4b was assigned based on 1H NMR spectra of the corresponding Mosher's diesters 5a-5c. Finally, the stereochemistry of the product 4a was confirmed by a single-crystal X-ray analysis of the corresponding dimesylate 6. To elucidate preferential formation of the weso-isomers, complexes of monohydroborated intermediate with borane were studied theoretically by DFT methods.
Renewable high-density spiro-fuels from lignocellulose-derived cyclic ketones
Xie, Junjian,Zhang, Xiangwen,Pan, Lun,Nie, Genkuo,Xiu-Tian-Feng,Liu, Qing,Wang, Peng,Li, Yafei,Zou, Ji-Jun
, p. 10303 - 10305 (2017/09/23)
Renewable high-density spiro-fuels are synthesized from lignocellulose-derived cyclic ketones for the first time, which show higher density, higher neat heat of combustion and lower freezing point compared with other biofuels synthesized from the same feedstock, and thus represent a new type of renewable high-density fuel attractive for practical applications.
Solid Acid-Catalyzed Dehydration of Pinacol Derivatives in Ionic Liquid: Simple and Efficient Access to Branched 1,3-Dienes
Hu, Yancheng,Li, Ning,Li, Guangyi,Wang, Aiqin,Cong, Yu,Wang, Xiaodong,Zhang, Tao
, p. 2576 - 2582 (2017/05/31)
The selective dehydration of pinacol derivatives to branched 1,3-dienes is extremely challenging because of the predominance of pinacol rearrangement. Herein, we successfully achieve this goal by employing a recyclable solid acid/ionic liquid catalyst system. The dehydration of alkyl- and cycloalkyl-derived diols in an Amberlyst-15/[Emim]Cl system afforded the corresponding 1,3-dienes in good yields, while a Nafion/[Emim]Cl system was demonstrated to be a better catalyst system for the dehydration of aryl-substituted substrates. Our protocol features straightforward and simple access to branched 1,3-dienes, high chemoselectivity, a recyclable catalyst system, a facile separation of dienes just by decantation, and a broad substrate scope.
Total synthesis and structural revision of vannusals A and B: Synthesis of the originally assigned structure of vannusal B
Nicolaou,Ortiz, Adrian,Zhang, Hongjun,Dagneau, Philippe,Lanver, Andreas,Jennings, Michael P.,Arseniyadis, Stellios,Faraoni, Raffaella,Lizos, Dimitrios E.
supporting information; experimental part, p. 7138 - 7152 (2010/07/09)
The total synthesis of the originally assigned structure of vannusal B (2) and its diastereomer (d-2) are described. Initial forays into these structures with model systems revealed the viability of a metathesis-based approach and a SmI2-mediated strategy for the key cyclization to forge the central region of the molecule, ring C. The former approach was abandoned in favor of the latter when more functionalized substrates failed to enter the cyclization process. The successful, devised convergent strategy based on the SmI 2-mediated ring closure utilized vinyl iodide (-)-26 and aldehyde fragment (±)-86 as key building blocks, whose lithium-mediated coupling led to isomeric coupling products (+)-87 and (-)-88 (as shown in Scheme 17 in the article). Intermediate (-)-88 was converted, via (-)-89 and (-)-90/(+)-91, to vannusal B structure 2 (as shown in Scheme 18 in the article), whose spectroscopic data did not match those reported for the natural product. Similarly, intermediate (+)-25, obtained through coupling of vinyl iodide (-)-26 and aldehyde (±)-27 (as shown in Scheme 13 in the article) was transformed via intermediates (-)-97 and (+)-98 (as shown in Scheme 19 in the article) to diastereomeric vannusal B structure (+)-d-2 (as shown in Scheme 19 in the article) which was also proven spectroscopically to be non-identical to the naturally occurring substance. These investigations led to the discovery and development of a number of new synthetic technologies that set the stage for the solution of the vannusal structural conundrum.
Total synthesis of the originally assigned structure of vannusal B
Nicolaou,Zhang, Hongjun,Ortiz, Adrian,Dagneau, Philippe
supporting information; experimental part, p. 8605 - 8610 (2009/05/15)
(Chemical Equation Presented) The truth is out there: The chase for the originally assigned structure of vannusal B (see structural formula) by total synthesis ended successfully, but created a new puzzle, that of the true structure of this intriguing marine natural product.
Study of I-strain relief in the intermediate when forming spiro ketones from unsymmetrical cycloalkylidenecycloalkanes, their dibromides, and their pinacols
Sands
, p. 468 - 471 (2007/10/02)
Three unsymmetrical intercyclic olefins, their dibromides, and their pinacols were prepared, each so the two carbons involved at the functional group were part of a different sized ring. The pinacols were reacted with 25% sulfuric acid and with boron trif
On the Rearrangement of a Tricyclic Unsaturated Ketone during Wolff-Kishner Reduction
Otterbach, Andreas,Musso, Hans
, p. 2257 - 2258 (2007/10/02)
Wolff-Kishner reduction of tricyclo2,5>dec-3-en-9-one (1) yields only 2-9percent of the expected olefin 7, 1-3percent of the syn isomer 8, but 17-26percent of bi(1-cyclopentenyl) (5).
On the Influence of Substituents on the Cope Rearrangement of 1,5-Hexadienes: Cyclopropyl- and Methyl-substituted Model Systems
Kaufmann, Dieter,Meijere, Armin de
, p. 1128 - 1138 (2007/10/02)
The new 1,5-hexadiene derivatives 1 and 2 are obtained along with all other conceivable products upon methylenation of 1,2,6,7-octatetraene (5); 2 is also accessible from succindialdehyde and cyclopropylidenetriphenylphosphorane.The thermal rearrangements of 1 and 2 both proceed like that of 5 in two steps via 1,4-cyclohexadiyls, 1 yielding 3 and 19, 2 only 4.The distinct differences in the gas phase kinetic parameters for 2 and 15 (ln k(2) = 22.0-26200/RT and ln k(15) = 29.1-33300/RT, respectively) indicate the change in mechanism of the Cope rearrangement from concerted (for 15) to stepwise (for 2), apparently due to the cyclopropyl substituent effects.Upon sensitized irradiation of 2 the new hydrocarbons 24, 25, and 27 are formed, whereas nickel(0)-catalyzed rearrangement of 2 yields 25 exclusively.
NICKEL-CATALYZED CROSS-COUPLING OF SILYL ENOL ETHERS WITH GRIGNARD REAGENTS. REGIO- AND STEREOCONTROLLED SYNTHESIS OF OLEFINS
Hayashi, Tamio,Katsuro, Yoshio,Kumada, Makoto
, p. 3915 - 3918 (2007/10/02)
The substitution of the siloxy group in silyl enol ethers with Grignard reagents to form olefins is accomplished by use of nickel acetylacetonate or phosphine-nickel complexes as catalysts, the stereo- and regiochemistry of coupled olefins depending upon the nature of the catalyst and reaction conditions employed.
