- Acid Chlorides as Formal Carbon Dianion Linchpin Reagents in the Aluminum Chloride-Mediated Dieckmann Cyclization of Dicarboxylic Acids
-
The development of acid chlorides as formal dianion linchpin reagents that enable access to cyclic 2-alkyl- and 2-acyl-1,3-alkanediones from dicarboxylic acids is described herein. Mechanistic experiments relying on 13C-labeling studies confirm the role of acid chlorides as carbon dianion linchpin reagents and have led to a revised reaction mechanism for the aluminum(III)-mediated Dieckmann cyclization of dicarboxylic acids with acid chlorides.
- Armaly, Ahlam M.,Bar, Sukanta,Schindler, Corinna S.
-
-
Read Online
- Design, synthesis and application of spiro[4.5]cyclohexadienonesviaone-pot sequentialp-hydroxybenzylation/oxidative dearomatization
-
One-pot sequentialp-hydroxybenzylation/oxidative dearomatization/spiroannulation has been designed for the efficient construction of tetrahydrofuran containing spiro-cyclohexadienones. This reaction proceeds through thep-hydroxybenzylation of 1,3-diketones withp-hydroxybenzyl alcoholviaquinone methide formation followed by oxidative dearomatization/spiroannulation with suitable alcohols. The Friedel-Crafts alkylation of spiro[4.5]cyclohexadienones with indoles provided a broad array of highly diastereoselective C-3 alkylated spirocycles and cyclohepta[b]indoles depending upon the ring size of the fused cyclic ketones.
- Patil, Vaibhav B.,Nanubolu, Jagadeesh Babu,Chegondi, Rambabu
-
supporting information
p. 5574 - 5577
(2021/06/12)
-
- Chemoselective Oxidation of Equatorial Alcohols with N-Ligated λ3-Iodanes
-
The site-selective and chemoselective functionalization of alcohols in complex polyols remains a formidable synthetic challenge. Whereas significant advancements have been made in selective derivatization at the oxygen center, chemoselective oxidation to the corresponding carbonyls is less developed. In cyclic systems, whereas the selective oxidation of axial alcohols is well known, a complementary equatorial selective process has not yet been reported. Herein we report the utility of nitrogen-ligated (bis)cationic λ3-iodanes (N-HVIs) for alcohol oxidation and their unprecedented levels of selectivity for the oxidation of equatorial over axial alcohols. The conditions are mild, and the simple pyridine-ligated reagent (Py-HVI) is readily synthesized from commercial PhI(OAc)2 and can be either isolated or generated in situ. Conformational selectivity is demonstrated in both flexible 1,2-substituted cyclohexanols and rigid polyol scaffolds, providing chemists with a novel tool for chemoselective oxidation.
- Mikhael, Myriam,Adler, Sophia A.,Wengryniuk, Sarah E.
-
supporting information
p. 5889 - 5893
(2019/08/26)
-
- Aluminum Chloride-Mediated Dieckmann Cyclization for the Synthesis of Cyclic 2-Alkyl-1,3-alkanediones: One-Step Synthesis of the Chiloglottones
-
Cyclic 2-alkyl-1,3-alkanediones are ubiquitous structural motifs in many natural products of biological importance. Reported herein is an AlCl3·MeNO2-mediated Dieckmann cyclization reaction of general synthetic utility that enables direct access to complex 2-alkyl-1,3-dione building blocks from readily available dicarboxylic acid and acid chloride substrates. This new strategy enables direct synthetic access to the chiloglottone plant pheromones from commercial material in a single synthetic transformation.
- Armaly, Ahlam M.,Bar, Sukanta,Schindler, Corinna S.
-
supporting information
p. 3958 - 3961
(2017/08/15)
-
- Method for preparing 2-methyl-1,3-dicarbonyl derivative
-
The invention discloses a method for preparing a 2-methyl-1,3-dicarbonyl derivative. A 1,3-dicarbonyl derivative serves as an initiator, raw materials are easy to obtain, and a great variety of raw materials are available. The product obtained through the method has high type diversity and can be used directly or used for other further reactions. Besides, only organic peroxides and a catalytic amount of inorganic copper salt are used, so that cost is low. According to the method, a reaction is conducted in air, reaction conditions are mild, pollution is small, reaction time is short, the yield of the target product is high, reaction operation and aftertreatment are easy, and the method is suitable for industrial production.
- -
-
Paragraph 0045
(2016/10/08)
-
- Efficient access to: cis -decalinol frameworks: copper(i)-catalyzed borylative cyclization of allene cyclohexanediones
-
Cu-catalyzed borylative cyclization of allene cyclohexanediones has been described through a tandem β-borylation and intramolecular allylic addition process, affording borylated cis-decalinols with excellent yields and diastereoselectivities. A good enantioselectivity is also achieved in the asymmetric version. The hemiboronate group in the cyclization products could be subjected to several useful transformations.
- Zhao, Yi-Shuang,Tang, Xiao-Qi,Tao, Jing-Chao,Tian, Ping,Lin, Guo-Qiang
-
supporting information
p. 4400 - 4404
(2016/06/06)
-
- First total synthesis of (+)-Carainterol A
-
The first, stereospecific, and elegant synthesis of the natural product (+)-Carainterol A was developed by using the Robinson annulation reaction as a key step to build the eudesmane sketeton.
- Ma, Kaiqing,Zhang, Chunbo,Liu, Mingming,Chu, Yong,Zhou, Lu,Hu, Changqi,Ye, Deyong
-
scheme or table
p. 1870 - 1872
(2010/09/07)
-
- CuH-catalyzed enantioselective 1,2-reductions of α,β-unsaturated ketones
-
The first study on a general technology for arriving at valued nonracemic allylic alcohols using asymmetric ligand-accelerated catalysis by copper hydride is described.
- Moser, Ralph,Boskovia, Zarko V.,Crowe, Christopher S.,Lipshutz, Bruce H.
-
supporting information; experimental part
p. 7852 - 7853
(2010/08/04)
-
- Synthesis of chiloglottones - Semiochemicals from sexually deceptive orchids and their pollinators
-
A five-step synthesis of monoalkyl- and 2,5-dialkyl-1,3-cyclohexanediones (1) is described via a sequence involving sequential Birch reductions and alkylations from the readily accessible and inexpensive starting material, 3,5-dimethoxybenzoic acid. Two approaches were considered in which alkylation at C-2 occurs either prior or subsequent to the proposed reduction. The successful route, in which Birch reduction of a 3-alkyl resorcinol derivative (3) precedes alkylation was applied in the synthesis of chiloglottone 1 (1dc), in 58% overall yield. Chiloglottone 1 is a member of a new class of natural products, representing a known sex pheromone of the thynnine wasp Neozeleboria cryptoides and pollinator attractant in the Australian sexually deceptive orchid genus Chiloglottis. The synthetic homologues were assessed for their biological activity via electroantennographic detection.
- Poldy, Jacqueline,Peakall, Rod,Barrow, Russell Allan
-
supporting information; experimental part
p. 4296 - 4300
(2009/12/06)
-
- Large-scale preparation of enantiomerically pure (4aR)-(-)-1,4a-dimethyl-4, 4a,7,8-tetrahydronaphthalene-2,5(3H,6H)-dione: A useful Wieland-Miescher diketone analogue
-
Wieland-Miescher diketone analogue 1 is a widely used precursor for asymmetric synthesis of natural sesquiterpenes and diterpenes. We describe here a large-scale preparation (>125 g batches) of enantiomerically pure compound 1 starting from propionyl chloride and using very simple and cheap reagents. A new one-pot sequence to the intermediate 2-methylcyclohexane-1,3-dione is also described. Georg Thieme Verlag Stuttgart.
- Lanfranchi, Don Antoine,Baldovini, Nicolas,Hanquet, Gilles
-
experimental part
p. 3775 - 3778
(2009/06/06)
-
- A brief and stereoselective synthesis of limonoid models, with antifeedant activity against Locusts migratoria
-
A short stereoselective preparation of havanensin-type limonoid models is reported. The synthesis is based on a radical domino reaction of an epoxyketone to a bicyclic hydroxyketone, and is achieved in six and nine steps from simple cyclohexenones. The epoxyhavanensin derivatives show significant antifeedant activity against Spodoptera littoralis and Spodoptera frugiperda, and the epoxyketone 21 shows potent antifeedant activity against Locusts migratoria.
- Fernández-Mateos,Ramos Silvo,Rubio González,Simmonds
-
p. 7809 - 7816
(2007/10/03)
-
- Concise access to indolizidine and pyrroloazepine skeleta via intramolecular Schmidt reactions of azido 1,3-diketones
-
Readily prepared 2-alkyl-2-azidopropylcycloalkyl-1,3-diones undergo intramolecular Schmidt rearrangement with a range of hard Lewis acids, leading to indolizidinediones and pyrroloazepinediones. Chiral aluminium-based Lewis acids could also be used to mediate this symmetry-breaking transformation, but no significant asymmetric induction was observed. The Royal Society of Chemistry 2006.
- Lertpibulpanya, Duanpen,Marsden, Stephen P.
-
p. 3498 - 3504
(2008/09/16)
-
- Asymmetric aza-Wittig reactions: Enantioselective synthesis of β-quaternary azacycles
-
A hindrance no more: The direct asymmetric synthesis of nitrogen heterocycles containing β-quaternary stereocenters, widely found for example in alkaloids, is highly challenging. The novel approach shown exploits the desymmetrization of prochiral diketo azides to unmask the asymmetric quaternary center, and represents the first reported examples of the asymmetric aza-Wittig reaction. (Chemical Equation Presented).
- Lertpibulpanya, Duanpen,Marsden, Stephen P.,Rodriguez-Garda, Ignacio,Kilner, Colin A.
-
p. 5000 - 5002
(2007/10/03)
-
- SAR studies of 3-cyclopropanecarbonyloxy-2-cyclohexen-1-one as inhibitors of 4-hydroxyphenylpyruvate dioxygenase
-
Various 3-cyclopropanecarbonyloxy-2-cyclohexen-1-one 1 derivatives have been synthesized and tested as inhibitors of 4-hydroxyphenylpyruvate dioxygenase (4-HPPD) from pig liver. The inhibition results indicated that well-positioned dicarbonyl groups as well as the cyclopropyl group of 1 were essential for potent inhibition. Substitution at the 2-position of the ring system has a significant effect on inhibitor potency, while the 5-position can undergo substantial variations and retain inhibitor potency. In the compounds examined, 2-chloro substituted 12 is the best inhibitor of all with IC50 of 15 nM, the rest of the synthesized analogues were less potent inhibitors than the parent compound.
- Lin, Yung-Lung,Wu, Chung-Shieh,Lin, Shean-Woei,Huang, Jian-Lin,Sun, Yang-Sheng,Yang, Ding-Yah
-
p. 685 - 690
(2007/10/03)
-
- Resonance energy of diradicals - 1,8-naphthoquinodimethane
-
From the racemization of 19c and the temperature and NO dependence of the trapping rate of 20b between 218 and 288°C the energy profile for the equilibrium 19b ? 20b is derived. The singlet-triplet splitting of the diradical is 2.5 kcal · mol-1 with the triplet being the ground state. By comparison of the experimental reaction enthalpy with the analogous value for 25, 26 or a hypothetical model reaction with non-interacting radicals it is shown that the stabilizing interaction of the radicals in the singlet state of 20b is negligible making the stabilization of the triplet equivalent to the singlet-triplet splitting. By using literature data it is shown by an analogous analysis that the interaction of the radicals in the bisallyl diradical 28 and in the triplet state of the trimethylenmethane derivative 29 is also negligible whereas in the singlet state of 29 the interaction is strongly destabilizing. VCH Verlagsgesellschaft mbH, 1996.
- Roth, Wolfgang R.,Unger, Christian,Wasser, Thorsten
-
p. 2155 - 2169
(2007/10/03)
-
- Substituent Effects on the CC Bond Strength, 16. - Thermal Stability and Enthalpies of Formation of β-Dicarbonyl Compounds. - Stabilisation Enthalpies of α,α'-Diketoalkyl Radicals
-
The geminal interactions of the two carbonyl groups in seven β-diketones of the type 8-9 and 11-13 were estimated from their enthalpies of formation, which were deduced from their heats of combustion and enthalpies of vaporization.The radical stabilisation enthalpies RSE of the α,α'-diketoalkyl radicals 9-13 were obtained from the enthalpies of activation ΔH(excit.) of thermal CC bond cleavage of eight model compounds of the type 9-13 by their comparison with ΔH(excit.) of comparable hydrocarbons of similar strain.For non-cyclic α,α'-diacylalkyl radicals and six-membered cyclic ones RSE = 54.8 +/- 1.3 kJ mol-1 was determined, which indicates an additive stabilisation by two carbonyl groups. - Key Words: Enthalpies of formation/ Geminal substituents, energetic interaction of/ Bond cleavage, C-C, kinetics of/ Radicals, stability of/ Increments, thermochemical/ Bond strength, substituent effects on
- Noelke, Margot,Verevkin, Sergej P.,Beckhaus, Hans-Dieter,Ruechardt, Christoph
-
-
- Process for producing 2-methyl-1,3-cyclohexanedione and 2-methylresorcinol
-
A process for producing 2-methyl-1,3-cyclohexanedione which comprises subjecting 1,3-cyclohexanedione, formaldehyde and a dialkylamine to Mannich reaction to obtain a 2-dialkylaminomethyl-1,3-cyclohexanedione, and subjecting the 2-dialkylaminomethyl to hydrogenolysis, and a process for producing 2-methylresorcinol which comprises aromatizing 2-methyl-1,3-cyclohexanedione obtained. According to these processes, it is possible to produce high-purity 2-methylresorcinol and 2-methyl-1,3-cyclohexanedione commercially easily and advantageously.
- -
-
-
- REGIOSELECTIVE SYNTHESIS OF TWO TYPES OF CYCLIC 3-(TRIMETHYLSILYLMETHYL)ENONES
-
Two types of cyclic 3-(trimethylsilylmethyl)enones were prepared selectively from the corresponding 1,3-diketones through 3-bromoenones or 3-siloxyenones.
- Horiguchi, Yoshiaki,Kataoka, Yasuhiro,Kuwajima, Isao
-
p. 3327 - 3330
(2007/10/02)
-
- Thiol esters in organic synthesis. XIV. The total synthesis of racemic α-costal
-
The first total synthesis of α-costal (1) in racemic form has been achieved in an unequivocal manner whereby the structure previously assigned to the natural aldehyde is confirmed.A salient feature of the synthesis is the use of S-tert-butyl cyanothiolacetate to facilitate the introduction of the labile acrolein unit.
- Liu, Hsing-Jang,Wynn, Hla
-
p. 658 - 666
(2007/10/02)
-
- Solvent Effects on Keto-Enol Equilibria: Tests of Quantitative Models
-
The effect of solvent on the equilibrium constants between selected keto-enol isomer pairs has been determined.The protomeric systems studied are 5,5-dimethyl-1,3-cyclohexanedione (1), 2-methyl-1,3-cyclohexanedione (3), 3-oxabicyclo-2,9-dioxononane (5), 2,4-pentanedione (7), ethyl 3-oxobutanoate (9), and 9-anthracenone (11).A wide variety of theoretical and empirical solvation parameters have been tested in a multiparameter linear free energy format to model the changes in equilibria.The most successful correlations are obtained with the Kamlet-Taft polarity-polarizability and hydrogen-bonding terms, although the Swain A and B factors have advantages in same cases.In general, for the isomer pairs in which the enol cannot form an internal hydrogen bond (1-2, 3-4, and 11-12), the equilibria appear to be controlled almost completely by the hydrogen-bonding basicity of the solvent.For the isomer pairs 5-6, 7-8, and 9-10, in which intramolecular hydrogen bonding is possible, the polarity-polarizability effect dominates, although differential stabilization of the isomers by hydrogen bonding remains significant.
- Mills, Sander G.,Beak, Peter
-
p. 1216 - 1224
(2007/10/02)
-
- Ring Cleavage of Cyclohexane-1,3-diones in the Aldol Cyclization Step of Robinson Annelations: A Novel Mechanism via Oxa-Twistanes and δ-Lactones
-
The pyrrolidine-induced aldol cyclization of methyl 2-methyl-2-(3-oxobutyl)-1,3-dioxocyclohexane-4-acetate (1) afforded methyl 1,2,3,4,6,7,8,8a-octahydro-8a-methyl-1,6-dioxonaphthalene-2-acetate (13) rather than undergoing lactonization-directed closure in the opposite sense.Mild base-induced cyclization of 1 with sodium methoxide in methanol or 1,8-diazabicycloundec-7-ene (DBU) in tetrahydrofuran (THF) effected cleavage of the cyclohexane-1,3-dione ring, giving mainly cyclohexenone acid 14a (2-(1,4-dimethyl-3-oxo-1-cyclohexen-2-ylmethyl)butanedioic acid monomethyl ester) and δ-lactone 15 (methyl (4aβ,8aβ)-octahydro-6,8a-dimethyl-2,5-dioxo-2H-1-benzopyran-4a-acetate).Prolonged exposure of 15 to sodium methoxide in methanol yielded mixtures of acyclic diester 17 and the isomeric γ-lactone 18 presumably via lactone methanolysis to ketol diester 16 followed by retroaldol ring opening or relactonization onto the acetate ester.The structure and stereochemistry of 18 were established by X-ray crystallography (Figure 1).Similar aldol cyclizations of 2-methyl-2-(3-oxobutyl)-1,3-cyclohexanedione (19) and its 4-methyl analogue (11) with sodium methoxide in methanol or DBU in THF afforded cyclohexenone acids 20a and 22a, respectively, the latter accompanied by δ-lactone 23.Bridged ketols 21 (from 19) and 24 and 25 (from 11) were also isolated from the reactions with DBU.A novel mechanism (Scheme I) involving bridging aldol cyclization to endo ketols (27 and 30), intramolecular hemiketal formation to oxatwistanones (28 and 31), ring cleavage to δ-lactones (29 and 32), and β-elimination of the δ-lactones having an available α-hydrogen to cyclohexenone acids is proposed to explain the formal retro-Claisen transformations in the absence of an external nucleophile (DBU/THF) and the apparent hydrolyses under anhydrous conditions.
- Muskopf, Jack W.,Coates, Robert M.
-
-
