105-30-6Relevant articles and documents
Hydroboration. 77. Revision of the Regioselectivity of the Hydroboration of Alkenes with Dihaloborane-Dimethyl Sulfide Complexes
Brown, Herbert C.,Racherla, Uday S.
, p. 895 - 897 (1986)
The hydroboration of alkanes with dihaloborane-dimethyl sulfide complexes (HBX2*SMe2, X = Cl, Br, and I) was systematically reexamined to establish the true regioselectivities in hydroboration with these reagents.Hydrogen halides (HX, X = Cl, Br, and I) liberated during the hydrolysis-oxidation of the alkyldihaloborane-dimethyl sulfide complexes (RBX2*SMe2) add to the residual alkene and hydrolyze to alcohols, thus introducing a significant error in the regioselectivity of such hydroborations.The true regioselectivities in the hydroboration of alkenes with HBX2*SMe2 reveal considerably smaller formation of secondary and tertiary derivatives than previously reported, a result that should significantly enhance the value of these hydroborating agents.
Total Synthesis and Structure Revision of Boholamide A
Han, Fangzhi,Liu, Guangju,Zhang, Xuhai,Ding, Yahui,Wang, Liang,Wu, Yijing,Chen, Yue,Zhang, Quan
, p. 4976 - 4980 (2021)
The 15-membered cyclic depsipeptide boholamide A and an epimer were prepared by total synthesis for the first time, thus leading to a revision of C6 stereochemistry in the originally proposed structure of natural boholamide A. This convergent route features achievement of a macro-lactamization step in a gram scale. The revised boholamide A was sythesized with 16 linear steps in 5.46% overall yield. This work facilitates the investigations of boholamide A as a potential hypoxia-selective anticancer agent.
Enantioselective Synthesis of the Proposed Structure of Santinol D
Xiong, Xin,Wu, Yikang,Liu, Bo
, p. 948 - 960 (2020)
In connection with structural verification of santinol D, a unique tricylglycerol isolated from Helichrysum italicum subsp. microphyllum, four possible isomers of its C-2'''and C-4''' centers were synthesized. The two enolizable chiral centers were installed with pre-defined absolute configurations using Evans alkylation and aldol condensation, respectively. The extra chiral center introduced in the aldol condensation was removed by Dess–Martin oxidation to convert the adjacent methine group into the highly enolizable subunit of an α-alkyl-β-keto ester at the end of the synthesis. The synthetic isomers provided unequivocal physical and NMR data for every single enantiomer and thus provided the information required for the configurational assignment of this natural product. With the aid of a model compound, the racemization of such species was examined polarimetrically under several sets of typical conditions and the rates were also calculated from the corresponding kinetics data.
ORGANOBORANES FOR SYNTHESIS. 5. STOICHIOMETRICALLY CONTROLLED REACTION OF ORGANOBORANES WITH OXYGEN UNDER MILD CONDITIONS TO ACHIEVE QUANTITATIVE CONVERSION TO ALCOHOLS
Brown, Herbert C.,Midland, M. Mark,Kabalka, George W.
, p. 5523 - 5530 (1986)
The reaction of organoboranes with oxygen under mild conditions can be controlled to give an essentially quantitative conversion of all three alkyl groups on boron to the corresponding alcohol.The controlled oxidation is a very clean reaction, with only minor amounts of carbonyl and hydrocarbon products formed.All organoboranes react quite rapidly in the initial stages, but vary considerably in the time required to achieve the desired uptake of oxygen.In contrast to oxidation by alkaline hydrogen peroxide, a portion of this reaction proceeds through alkyl radicals, thus resulting in some loss of stereospecificity.Oxidation of mixed organoboranes reveals that the relative rates of oxidation of alkyl groups on boron are consistent with a radical mechanism, with tertiary > secondary > primary in the rate of oxidation.The selective oxidation of one alkyl group in the presence of the other is not possible, due to small differences in relative rates of oxidation.However, thexyl and cyclohexyl groups can be selectively removed from boron in the presence of alkenyl groups.Thus, controlled oxidation of thexyldialkenylborane affords pure dialkenylborinic acid.
A Specific Blend of Drakolide and Hydroxymethylpyrazines: An Unusual Pollinator Sexual Attractant Used by the Endangered Orchid Drakaea micrantha
Bohman, Bj?rn,Tan, Monica M. Y.,Phillips, Ryan D.,Scaffidi, Adrian,Sobolev, Alexandre N.,Moggach, Stephen A.,Flematti, Gavin R.,Peakall, Rod
, p. 1124 - 1128 (2020)
Bioactive natural products underpin the intriguing pollination strategy used by sexually deceptive orchids. These compounds, which mimic the sex pheromones of the female insect, are emitted in particular blends to lure male insect pollinators of specific species. By combining methods from field biology, analytical chemistry, electrophysiology, crystallography, and organic synthesis, we report that an undescribed β-hydroxylactone, in combination with two specific hydroxymethylpyrazines, act as pollinator attractants in the rare hammer orchid Drakaea micrantha. This discovery represents an unusual case of chemically unrelated compounds being used together as a sexual attractant. Furthermore, this is the first example of the identification of pollinator attractants in an endangered orchid, enabling the use of chemistry in orchid conservation. Our synthetic blend is now available to be used in pollinator surveys to locate suitable sites for plant conservation translocations.
ORGANOBORANES FOR SYNTHESIS. 6. A CONVENIENT, GENERAL SYNTHESIS OF ALKYLHYDROPEROXIDES via AUTOXIDATION OF ORGANOBORANES
Brown, Herbert C.,Midland, M. Mark
, p. 4059 - 4070 (1987)
The low temperature autoxidation of organoboranes in tetrahydrofuran leads to the formation of diperoxyboranes, which provide the corresponding alkylhydroperoxides in excellent yields, upon treatment with hydrogen peroxide.However, only two of the three alkyl groups on boron are used for the formation of hydroperoxides.This difficulty was solved by employing alkyldichloroborane etherates instead of trialkylboranes.The alkyldichloroborane etherates react cleanly with one molar equivalent of oxygen in ether solvent.The product is readily hydrolyzed to form the corresponding hydroperoxides in excellent yields.The autoxidation of organoboranes is inhibited by iodine or such free-radical scavengers.A study of the inhibition by iodine of the oxidation of representative trialkylboranes indicates that the rate of initiation decreases with an increase in the steric crowding about the boron atom.The rate of inhibition of the autoxidation of trialkylboranes by iodine reveals that the reaction involves a relatively slow rate of radical initiation, followed by a very fast rate of chain propagation.
Cp2TiCl2-catalyzed grignard reactions. 2. Reactions with ketones and aldehydes
Sato, Fumie,Jinbo, Takamasa,Sato, Masao
, p. 2171 - 2174 (1980)
The reaction of Grignard reagents with ketones or aldehydes in the presence of a catalytic amount of Cp2TiCl2 leads to the corresponding reduction products in high yields. Cp2TiH intermediate was proposed to account for this observation.
Widely applicable synthesis of enantiomerically pure tertiary alkyl-containing 1-alkanols by zirconium-catalyzed asymmetric carboalumination of alkenes and palladium- or copper-catalyzed cross-coupling
Xu, Shiqing,Lee, Ching-Tien,Wang, Guangwei,Negishi, Ei-Ichi
, p. 1829 - 1835 (2013)
A highly enantioselective and widely applicable method for the synthesis of various chiral 2-alkyl-1-alkanols, especially those of feeble chirality, has been developed. It consists of zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA), lipase-catalyzed acetylation, and palladium- or copper-catalyzed cross-coupling. By virtue of the high selectivity factor (E) associated with iodine, either (S)- or (R)-enantiomer of 3-iodo-2-alkyl-1- alkanols (1), prepared by ZACA reaction of allyl alcohol, can be readily purified to the level of ≥99 % ee by lipase-catalyzed acetylation. A variety of chiral tertiary alkyl-containing alcohols, including those that have been otherwise difficult to prepare, can now be synthesized in high enantiomeric purity by Pd- or Cu-catalyzed cross-coupling of (S)-1 or (R)-2 for introduction of various primary, secondary, and tertiary carbon groups with retention of all carbon skeletal features. These chiral tertiary alkyl-containing alcohols can be further converted into the corresponding acids with full retention of the stereochemistry. The synthetic utility of this method has been demonstrated in the highly enantioselective (≥99 % ee) and efficient syntheses of (R)-2-methyl-1-butanol and (R)- and (S)-arundic acids. Look, mom, one hand! 2-Alkyl-1-alkanols of feeble chirality have been synthesized by a sequence of zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA), lipase-catalyzed acetylation, and Pd- or Cu-catalyzed cross-coupling in high enantiomeric purity of ≥99 % ee. The synthetic utility of this method has been demonstrated in highly enantioselective and efficient syntheses of (R)-2-methyl-1-butanol, (R)- and (S)-arundic acids. Copyright
Synthesis and fungicidal activity of 2-methylalkyl isonicotinates and nicotinates
Huras, Bogumi?a,Zakrzewski, Jerzy,Krawczyk, Maria,Bombińska, Danuta,Cieniecka-Ros?onkiewicz, Anna,Michalczyk, Alicja
, p. 509 - 517 (2017)
Abstract: Homologs and analogs of 2-methylheptyl isonicotinate (new, natural antifungal and antibacterial antibiotic isolated from Streptomyces sp. 201): racemic 2-methylalkyl isonicotinates 4 and nicotinates 5 and enantiomerically enriched in the R and S isomers, 2-methylpentyl isonicotinate and nicotinate were obtained. Fungistatic activity of the compounds was evaluated. Nicotinates 5a–c show significant activity against phytopathogenic fungi: Fusarium culmorum, Phytophthora cactorum, Rhizoctonia solani. The activity of the enantiomerically enriched compounds was comparable to the activity of racemic ones. There was no significant difference in fungistatic activity between the enantiomerically enriched R and S isomers. Investigated compounds and their oxalates have proven to be active against chalkbrood disease caused by fungal species Ascosphaera apis. The activity of the nicotinates 5a and 5b and oxalates 5a–c against Ascosphaera apis was higher than the activity of oxalic acid itself. Especially high activity was shown for 2-methylbutyl nicotinate 5a and oxalate of 2-methylpentyl nicotinate 5b. Graphical abstract: [InlineMediaObject not available: see fulltext.]
Characterization of active sites over reduced Ni-Mo/Al2O 3 catalysts for hydrogenation of linear aldehydes
Wang, Xueqin,Ozkan, Umit S.
, p. 1882 - 1890 (2005)
Reduced Ni-Mo/Al2O3 catalysts exhibit a behavior analogous to that of sulfided Ni-Mo/Al2O3 catalysts in hydrogenation of linear aldehydes to alcohols. Similar to what has been previously reported for sulfided catalysts, NO and CO2 can be used over the reduced Ni-Mo catalysts as probe molecules for the active sites responsible for two competing reactions - aldehyde hydrogenation to alcohols and condensation reactions to heavy products, respectively. Reduced catalysts have a higher aldehyde conversion activity and alcohol selectivity than their sulfided counterparts. The reduction temperature has a strong effect on the surface density of anion vacancies, which are responsible for alcohol formation. Reduction temperature also plays a role in determining the abundance of OH groups on the alumina surface. The effect of reduction temperature also manifests itself through the differences seen in the oxidation states of Mo and Ni species.
