- Organocatalytic, Organic Oxidant Promoted, Enamine C?H Oxidation/Cyclopropanation Reaction
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Herein, we demonstrate that organic, single-electron oxidant in the presence of diarylprolinol silylether type catalyst serves as a tool for the transformation of electron-rich enamines to iminium ions. These iminium ions take part in a subsequent Michael-initiated ring-closure (MIRC) reaction with in situ present nucleophile giving rise to overall cyclopropanation reaction of saturated aldehydes. Stereodefined cyclopropanes are obtained in high yields and selectivities. This one-pot transformation represents the additional example of saturated aldehydes being used in the coupled one-pot processes. (Figure presented.).
- Bond?i?, Aleksandra M.,Bond?i?, Bojan P.,D?ambaski, Zdravko,Kokotos, Christoforos G.,Triandafillidi, Ierasia
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supporting information
p. 4002 - 4008
(2021/07/06)
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- Rhodium-Catalyzed Remote C(sp3)?H Borylation of Silyl Enol Ethers
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A rhodium-catalyzed remote C(sp3)?H borylation of silyl enol ethers (SEEs, E/Z mixtures) by alkene isomerization and hydroboration is reported. The reaction exhibits mild reaction conditions and excellent functional-group tolerance. This method is compatible with an array of SEEs, including linear and branched SEEs derived from aldehydes and ketones, and provides direct access to a broad range of structurally diverse 1,n-borylethers in excellent regioselectivities and good yields. These compounds are precursors to various valuable chemicals, such as 1,n-diols and aminoalcohols.
- Li, Jie,Qu, Shuanglin,Zhao, Wanxiang
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p. 2360 - 2364
(2020/01/02)
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- Rh(I)-catalyzed ring-opening of cyclobutanols via C–C bond activation: Synthesis of cis-olefin with a remote aldehyde
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A Rh(I)-catalyzed ring-opening of cyclobutanols has been developed with ring opening products bearing cis-olefin and a remote aldehyde. Various substrates bearing different substituted aryl groups, heterocyclic groups and alkyl groups were compatible with
- Nie, Yu,Chen, Jianzhong,Zhang, Wanbin
-
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- Enantioselective Organocatalytic Enamine C?H Oxidation/Diels- Alder Reaction
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α,β-unsaturated aldehydes have been traditionally used in LUMO lowering asymmetric aminocatalysis (iminium catalysis), while the use of saturated aldehydes as substrates in this type of catalysis has been elusive, until recently. Herein, we demonstrate that organic, single-electron oxidants in the presence of diarylprolinol silylether type catalysts serve as effective tools for the transformation of electron rich enamines to iminium ions which partake in a subsequent Diels-Alder reaction. This enantioselective one-pot transformation represents the first example of saturated aldehydes being used in domino Diels-Alder reaction processes and demonstrates the power of this protocol for construction of stereo-defined chiral compounds and building blocks. (Figure presented.).
- D?ambaski, Zdravko,Tzaras, Dimitrios-Ioannis,Lee, Sunggi,Kokotos, Christoforos G.,Bondzic, Bojan P.
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p. 1792 - 1797
(2019/02/25)
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- Stereospecific Alkene Aziridination Using a Bifunctional Amino-Reagent: An Aza-Prilezhaev Reaction
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In situ deprotection (TFA) of O-Ts activated N-Boc hydroxylamines triggers intramolecular aziridination of N-tethered alkenes to provide complex N-heterocyclic ring systems. Synthetic and computational studies corroborate a diastereospecific aza-Prilezhaev-type mechanism. The feasibility of related intermolecular alkene aziridinations is also demonstrated.
- Farndon, Joshua J.,Young, Tom A.,Bower, John F.
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supporting information
p. 17846 - 17850
(2019/01/04)
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- Pd(II)-Catalyzed [4 + 2] Heterocyclization Sequence for Polyheterocycle Generation
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A new Pd(II)-catalyzed cascade sequence for the formation of polyheterocycles, from simple starting materials, is reported. The sequence is applicable to both indole and pyrrole substrates, and a range of substituents are tolerated. The reaction is thought to proceed by a Pd(II)-catalyzed C-H activated Heck reaction followed by a second Pd(II)-catalyzed aza-Wacker reaction with two Cu(II)-mediated Pd(0) turnovers per sequence. The sequence can be considered a formal [4 + 2] heterocyclization.
- Glaisyer, Elizabeth L.,Watt, Michael S.,Booker-Milburn, Kevin I.
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supporting information
p. 5877 - 5880
(2018/09/25)
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- C(alkenyl)-H Activation via Six-Membered Palladacycles: Catalytic 1,3-Diene Synthesis
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A catalytic method to prepare highly substituted 1,3-dienes from two different alkenes is described using a directed, palladium(II)-mediated C(alkenyl)-H activation strategy. The transformation exhibits broad scope across three synthetically useful substrate classes masked with suitable bidentate auxiliaries (4-pentenoic acids, allylic alcohols, and bishomoallylic amines) and tolerates internal nonconjugated alkenes, which have traditionally been a challenging class of substrates in this type of chemistry. Catalytic turnover is enabled by either MnO2 as the stoichiometric oxidant or co-catalytic Co(OAc)2 and O2 (1 atm). Experimental and computational studies were performed to elucidate the preference for C(alkenyl)-H activation over other potential pathways. As part of this effort, a structurally unique alkenylpalladium(II) dimer was isolated and characterized.
- Liu, Mingyu,Yang, Pusu,Karunananda, Malkanthi K.,Wang, Yanyan,Liu, Peng,Engle, Keary M.
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p. 5805 - 5813
(2018/05/14)
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- Aerobic Photooxidative Synthesis of β-Alkoxy Monohydroperoxides Using an Organo Photoredox Catalyst Controlled by a Base
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Transition-metal-free synthesis of β-alkoxy monohydroperoxides via aerobic photooxidation using an acridinium photocatalyst was developed. This method enables the synthesis of some novel hydroperoxides. The peroxide source is molecular oxygen, which is cost-effective and atomically efficient. Magnesium oxide plays an important role as a base in the catalytic system.
- Asano, Yuya,Nagasawa, Yoshitomo,Yamaguchi, Eiji,Itoh, Akichika
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p. 409 - 412
(2018/02/21)
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- Synthesis of ent-[3]-Ladderanol: Development and Application of Intramolecular Chirality Transfer [2+2] Cycloadditions of Allenic Ketones and Alkenes
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An enantioselective synthesis of ent-[3]-ladderanol is presented. The ladderanes are an interesting class of molecules for their unique structure of fused cyclobutane rings as well as their perceived biological function of organism protection. The route h
- Line, Nathan J.,Witherspoon, Brittany P.,Hancock, Erin N.,Brown, M. Kevin
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supporting information
p. 14392 - 14395
(2017/10/24)
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- Regioselective Epoxidations by Cytochrome P450 3A4 Using a Theobromine Chemical Auxiliary to Predictably Produce N-Protected β- or γ-Amino Epoxides
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N-Protected β- and γ-amino epoxides are useful chiral synthons. We report here that the enzyme cytochrome P450 3A4 can catalyze the formation of such compounds in a regio- and stereoselective manner, even in the presence of multiple double bonds or aromatic substituents. To this end, the theobromine chemical auxiliary is used not only to control the selectivity of the enzyme, but also as a masked amine, and to facilitate product recovery. Theobromine predictably directed epoxidation at the double bond of the fourth carbon from the theobromine group. Unlike with most catalysts, the selectivity did not depend on electronic or steric factors but rather on the position of the olefin relative to the theobromine group. (Figure presented.).
- Polic, Vanja,Cheong, Kin Jack,Hammerer, Fabien,Auclair, Karine
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p. 3983 - 3989
(2017/11/30)
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- Palladium-Catalyzed Aerobic Oxidative Cyclization of Aliphatic Alkenyl Amides for the Construction of Pyrrolizidine and Indolizidine Derivatives
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An efficient palladium-catalyzed aerobic oxidative cyclization has been developed to synthesize a variety of pyrrolizidine and indolizidine derivatives from simple aliphatic alkenyl amides in moderate to good yields. The reaction features the capability of accessing various N-heterocycles and the use of molecular oxygen (1 atm) as the green oxidant.
- Lo, Kai-Yip,Ye, Liu,Yang, Dan
-
supporting information
p. 1570 - 1575
(2017/08/11)
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- Ni-Catalyzed regio- and stereoselective addition of arylboronic acids to terminal alkynes with a directing group tether
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Addition of arylboronic acids to directing group tethered acetylenes in a regio and stereoselective manner using an inexpensive catalytic system is achieved for the first time to access highly sought after allyl/homoallyl alcohol/amine units. The apparent vinylnickel intermediate was successfully trapped by the Michael electrophiles to get defined tri- and tetra-substituted olefins. An interesting selectivity switch was observed with internal alkynes.
- Hari Babu, Madala,Ranjith Kumar, Gadi,Kant, Ruchir,Sridhar Reddy, Maddi
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supporting information
p. 3894 - 3897
(2017/04/04)
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- Copper-Catalyzed Diastereoselective Synthesis of Trifluoromethylated Tetrahydrofurans
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The copper-catalyzed intramolecular diastereoselective trifluoromethylcycloetherification of homoallylic alcohols with Togni's reagent as trifluoromethylating reagent was realized under mild conditions. Various trifluoromethylated tetrahydrofurans were synthesized in moderate to good yields. Moreover, a wide range of common functional groups was tolerated.
- Wang, Yanan,Jiang, Min,Liu, Jin-Tao
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supporting information
p. 1322 - 1327
(2016/04/26)
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- Ni-catalyzed stereoselective arylation of inert C-O bonds at low temperatures
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A Ni-catalyzed arylation of inert C-O bonds that operates at temperatures as low as -40 C is described. Unlike other methods for C-O bond cleavage utilizing organometallic species, this protocol operates at low temperatures, thus allowing the presence of sensitive functional groups with exquisite site-selectivity and stereoselectivity.
- Cornella, Josep,Martin, Ruben
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supporting information
p. 6298 - 6301
(2014/01/17)
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- Selective synthesis of unsymmetrical ethers from different alcohols catalyzed by sodium bisulfite
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An efficient method for the preparation of unsymmetrical ethers from alcohols catalyzed by sodium bisulfite is reported. The procedure enables the direct dehydration of primary, secondary, and tertiary benzylic alcohols with aliphatic alcohols in the abse
- Yu, Jun-Lai,Wang, Hui,Zou, Kai-Feng,Zhang, Jia-Rui,Gao, Xiang,Zhang, Dan-Wei,Li, Zhan-Ting
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p. 310 - 315
(2013/01/15)
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- Manganese(III) acetate mediated oxidative radical cyclizations. Toward vicinal all-carbon quaternary stereocenters
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Manganese(III) acetate mediated oxidative radical cyclizations have been used to synthesize a range of densely functionalized and sterically congested cyclopentane-lactones. A number of the resulting lactones contain vicinal all-carbon quaternary stereocenters adjacent to a tertiary benzylic stereocenter and are formed with high levels of stereocontrol.
- Logan, Angus W.J.,Parker, Jeremy S.,Hallside, Michal S.,Burton, Jonathan W.
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supporting information; experimental part
p. 2940 - 2943
(2012/08/28)
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- Copper-catalyzed highly selective semihydrogenation of non-polar carbon-carbon multiple bonds using a silane and an alcohol
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A copper catalyst bearing a suitable Xantphos derivative or NHC ligand was found to be highly efficient for the selective semihydrogenation of non-polar unsaturated compounds using a mixture of a silane and an alcohol as reducing agent. The catalytic system was useful for the selective semihydrogenation of internal alkynes to (Z)-alkenes with suppression of overreduction to the corresponding alkanes. Furthermore, semihydrogenations of terminal alkyne, 1,2-diene, 1,3-diene, 1,3-enyne and 1,3-diyne systems were also achieved selectively. Copyright
- Semba, Kazuhiko,Fujihara, Tetsuaki,Xu, Tinghua,Terao, Jun,Tsuji, Yasushi
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supporting information; experimental part
p. 1542 - 1550
(2012/08/08)
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- Introducing a mixed-valent dirhodium(ii,iii) catalyst with increased stability in C-H amination
-
A new mixed-valent Rh2II,III dimer, [Rh 2(espn)2Cl] (espn2- = α,α, α′,α′-tetramethyl-1,3-benzenedipropanamidate), is reported. This compound readily dissociates Cl- at low concentrations in solution to form the active [Rh2(espn)2]+ catalyst, which performs intramolecular C-H amination with TONs > 1400. This work expands the scope of Rh2II,III dimers to nitrenoid chemistry.
- Kornecki, Katherine P.,Berry, John F.
-
supporting information
p. 12097 - 12099
(2013/01/16)
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- O-alkyl-N-acyl-N-phenylhydroxylamines as photochemical alkoxy radical precursors
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A simple and efficient technique for the photolysis of alkoxy radical precursors is developed. Irradiation of O-alkyl-N-acyl-N-phenylhydroxylamines, as representative alkoxy radical precursors, with ultraviolet light (254 nm) results in homolytic N-O bond cleavage to generate singlet alkoxy and acylaminyl caged radical pairs. These radicals, depending on the solvent employed, either escape from the cage to form fragmentation products, or undergo in-cage reactions to produce photorearrangement products. The homolytic cleavage of the N-O bond is analyzed using time-dependent density functional theory calculations. The nature of the N-acyl substituent on the O-alkyl-N-acyl-N- phenylhydroxylamines is shown to influence their ability to generate radicals. Furthermore, identification and trapping of the alkoxy radicals is demonstrated. Georg Thieme Verlag Stuttgart · New York.
- Chowdhury, Nilanjana,Anoop, Anakuthil,Singh, N.D. Pradeep
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experimental part
p. 1745 - 1754
(2012/07/27)
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- Metal-free oxyaminations of alkenes using hydroxamic acids
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A radical-mediated approach to metal-free alkene oxyamination is described. This method capitalizes on the unique reactivity of the amidoxyl radical in alkene additions to furnish a general difunctionalization using simple diisopropyl azodicarboxylate (DIAD) as a radical trap. This protocol capitalizes on the intramolecular nature of the process, providing single regioisomers in all cases. Difunctionalizations of cyclic alkenes provide trans oxyamination products inaccessible using current methods with high levels of stereoselectivity, complementing cis-selective oxyamination processes.
- Schmidt, Valerie A.,Alexanian, Erik J.
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supporting information; scheme or table
p. 11402 - 11405
(2011/09/16)
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- Nickel-catalyzed allylic substitution of simple alkenes
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This report describes a nickel-catalyzed allylic substitution process of simple alkenes whereby an important structural motif, a 1,4-diene, was prepared. The key to success is the use of an appropriate nickel-phosphine complex and a stoichiometric amount of silyl triflate. Reactions of 1-alkyl-substituted alkenes consistently provided 1,1-disubstituted alkenes with high selectivity. Insight into the reaction mechanism as well as miscellaneous application of the developed catalytic process is also documented.
- Matsubara, Ryosuke,Jamison, Timothy F.
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supporting information; scheme or table
p. 1860 - 1875
(2012/02/02)
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- Palladium-catalyzed carbonylative heck-type reactions of alkyl iodides
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A palladium-catalyzed carbonylative Heck-type cyclization of alkyl halides is described. Treatment of a range of primary and secondary alkyl iodides with catalytic palladium(0) under CO pressure forms a variety of synthetically versatile enone products. The reactivity described represents a rare example of a palladium-catalyzed Heck-type cyclization involving unactivated alkyl halides with β-hydrogens. Alkene substitution is well tolerated, and mono-and bicyclic carbocycles may be easily accessed.
- Bloome, Kayla S.,Alexanian, Erik J.
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supporting information; experimental part
p. 12823 - 12825
(2010/11/03)
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- Intramolecular anodic olefin coupling reactions and the synthesis of cyclic amines
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Anodic olefin coupling reactions using a tosylamine trapping group have been studied. The cyclizations are favored by the use of a less-polar radical cation and more basic reaction conditions. The most significant factor for obtaining good yields of cyclic product is the use of the more basic reaction conditions. However, a number of factors including the nature of both the solvent and the electrolyte used can influence the yield of the cyclizations. The cyclizations allow for the rapid synthesis of both substituted proline and pipecolic acid type derivatives.
- Xu, Hai-Chao,Moeller, Kevin D.
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supporting information; experimental part
p. 2839 - 2844
(2010/06/11)
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- Intramolecular anodic olefin coupling reactions: The use of a nitrogen trapping group
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Anodic olefin coupling reactions using a tosylamine trapping group have been studied. The cyclizations are favored by the use of a less-polar radical cation and more basic reaction conditions. The most significant factor for obtaining good yields of cyclic product is the use of the more basic reaction conditions. The cyclizations allow for the rapid synthesis of substituted proline derivatives. Copyright
- Xu, Hai-Chao,Moeller, Kevin D.
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supporting information; experimental part
p. 13542 - 13543
(2009/02/06)
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- Two-faced reactivity of alkenes: cis- versus trans-aminopalladation in aerobic Pd-catalyzed intramolecular Aza-Wacker reactions
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A number of different PdII catalyst systems have been reported recently for the Wacker-type aerobic oxidative cyclization of alkenes bearing tethered nitrogen nucleophiles. This study examines the stereochemistry of the aminopalladation step wi
- Liu, Guosheng,Stahl, Shannon S.
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p. 6328 - 6335
(2008/02/03)
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- One-pot regio- and stereoselective cyclization of 1,2,n-triols
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A simple and efficient process to cyclize triols containing a 1,2-diol functionality with a pendant hydroxyl group is presented. The one-pot procedure converts the 1,2-diol into an ortho ester in situ, which upon treatment with a Lewis acid generates a cyclic acetoxonium intermediate. This intermediate is subsequently trapped by the pendant hydroxyl group to generate a cyclic ether. The stereochemistry of the 1,2-diol is transferred to the product with complete fidelity (inversion at the site of cyclization), and the reaction proceeds with high regioselectivity. The process is akin to the Lewis acid-catalyzed intramolecular ring-opening of epoxides with hydroxyl groups yielding cyclic ethers of various sizes with regio- and stereochemical control. Copyright
- Zheng, Tao,Narayan, Radha S.,Schomaker, Jennifer M.,Borhan, Babak
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p. 6946 - 6947
(2007/10/03)
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- Synthesis of 2-phenyl-2-cycloalkenones via palladium-catalyzed tandem epoxide isomerization-intramolecular aldol condensation
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We have extended the scope of our palladium-catalyzed tandem epoxide isomerization/aldol condensation reaction to encompass intramolecular condensations, which provide facile access to conjugated cycloalkenones from epoxy aldehydes or diepoxides. For example, reaction of 5,6-epoxy-6- phenylhexanal with Pd(OAc)2-PBu3 catalyst in the presence of NaHCO3 and 3A molecular sieves forms 2-phenyl-2-cyclopentenone (80%). Similarly, 1,2;5,6-diepoxy-1-phenylhexane affords 3-methyl-2-phenyl-2-cyclopentenone (72%). The observation of dicarbonyl intermediates (e.g., 1-phenyl-2,5- hexanedione in the latter case) demonstrates that the reaction proceeds via Pd-catalyzed isomerization of the diepoxide to the diketone, followed by base-catalyzed aldol condensation.
- Kim, Ji-Hyun,Kulawiec, Robert J.
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p. 3107 - 3110
(2007/10/03)
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- ATP-citrate lyase as a target for hypolipidemic intervention. Design and synthesis of 2-substituted butanedioic acids as novel, potent inhibitors of the enzyme
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ATP-citrate lyase is the primary enzyme responsible for the synthesis of cytosolic acetyl-CoA in many tissues. Inhibitors of the enzyme represent a potentially novel class of hypolipidemic agent, which are anticipated to have combined hypocholesterolemic and hypotriglyceridemic properties. A series of 2-substituted butanedioic acids have been designed and synthesized as inhibitors of the enzyme. The best compounds, 58, 68, 71, 74 have reversible K(i)'s in the 1-3 μM range against the isolated rat enzyme. As representative of this compound class, 58, has been shown to exert its inhibitory action through a mainly competitive mechanism with respect to citrate and a noncompetitive one with respect to CoA. None of the inhibitors were able to inhibit cholesterol and/or fatty acid synthesis in HepG2 cells. This has been attributed to the adverse physicochemical properties of the molecules leading to a lack of cell penetration. Despite this, a lead structural class of compound has been identified with the potential for modification into potent, cell-penetrant, and efficacious inhibitors of ATP- citrate lyase.
- Gribble, Andrew D.,Dolle, Roland E.,Shaw, Antony,McNair, David,Novelli, Riccardo,Novelli, Christine E.,Slingsby, Brian P.,Shah, Virendra P.,Tew, David,Saxty, Barbara A.,Allen, Mark,Groot, Pieter H.,Pearce, Nigel,Yates, John
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p. 3569 - 3584
(2007/10/03)
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- Nucleophile-induced ring enlargement of 1-(1-iodoalkyl)silacyclobutane and 1-(1,2-epoxyalkyl)silacyclobutane into silacyclopentane. Application to the synthesis of 1,4-diol, 4-alken-1-ol, and 1,4,5-triol
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Two methods for ring enlargement of silacyclobutane into silacyclopentane have been described. (1) Treatment of 1-(1-iodoalkyl)silacyclobutane with t-BuOK or AgOAc provided 2-alkyl-1-silacyclopentanes which were easily converted into 1,4-diols by oxidativ
- Matsumoto,Takeyama,Miura,Oshima,Utimoto
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p. 250 - 261
(2007/10/02)
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- Lithium Carbenoids Induced Ring Enlargement of Silicacyclobutane into 2-Halo-1-silacyclopentane and its Use in Organic Synthesis
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An addition of lithium diisopropylamide to a solution of 1,1-dimethyl-1-silacyclobutane and dihalometane such as CH2I2, CH2Br2, or CH2Cl2 provided the corresponding 1,1-dimethyl-2-halo-1-silacyclopentane in good yield.The reactions of 1,1,2-trimethyl-1-si
- Matsumoto, Kozo,Aoki, Yoshitaka,Oshima, Koichiro,Utimoto, Kiitiro
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p. 8487 - 8502
(2007/10/02)
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- Base-induced rearrangement of oxiranylsilacylobutane into silacyclopentane. Application to stereoselective synthesis of 4-alken-1-ol and 1,4,5-triol
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Treatment of 1-methyl-1-(cis-1,2-epoxyhexyl)-1-silacyclobutane 16a with i-PrOLi provided erythro-1-methyl-1-isopropoxy-2-(2-hydroxypentyl)-1-silacyclopentane 17a which was converted into (Z)-4-nonen-1-ol 18, (E)-4-nonen-1-ol 19, or 1,4,5-nonanetriol 20, r
- Matsumoto,Takeyama,Oshima,Utimoto
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p. 4545 - 4548
(2007/10/02)
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- Intramolecular cyclization of acetylenic homoallylic ketones mediated by the addition of stannyl radicals; a short facile pathway to α-methylene-β-substituted cyclopentanones
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α-(Stannyl)methylenecyclopentanones are obtained by tributylstannane addition reactions of acetylenic homoallylic ketones. α-Methylenecyclopentanones are produced upon destannylation.
- Lee,Hur,Park
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p. 7219 - 7220
(2007/10/02)
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- A NOVEL CYCLIZATION REACTION OF OXIDO DIAZOALKANES: FORMATION OF 1-SUBSTITUTED CYCLOALKENES
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The thermal decomposition of dialkali metal salts of δ-hydroxybutyl ketone and ε-hydroxypentyl ketone tosylhydrazones in diglyme at 80-120 deg C produced the 1-substituted cyclopentene and cyclohexene, respectively.
- Harada, Toshiro,Akiba, Eiji,Oku, Akira
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p. 651 - 654
(2007/10/02)
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- Cycloaddition Reactions of Strained Ring Systems. Photosensitized Cycloadditions of 2-(Acyloxy)-Substituted Cyclopropenes
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The sensitized photocycloaddition reaction of 1-phenyl-2-carbomethoxy-3,3-dimethylcyclopropene with a series of phenyl-substituted olefins has been investigated.The photocycloaddition is sensitive to steric factors with the reactants approaching eac
- Padwa, Albert,Kennedy, G. Davon,Wannamaker, M. Woods
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p. 5334 - 5341
(2007/10/02)
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- Transformation of Carbon-Oxygen into Carbon-Carbon Bonds Mediated by Low-Valent Nickel Species
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The substitution of alkoxy groups of enol ethers (1-methoxycyclohexenes, 1-methoxy-1-alkenes, and benzofuran) and aryl ethers (methoxynaphthalenes, cresyl methyl ethers, and dimethoxybenzenes) by hydrogen, alkyl groups, and aryl units, through Grignard reactions catalyzed by bis(triphenylphosphine)nickel dichloride or nickel dichloride, is described.The stereochemistry of the new reaction is portrayed, especially in connection with processes involving ring opening of dihydropyrans and dihydrofurans.The reaction has been applied to the synthesis of a termite trail pheromone and the acetate of the Douglas fir beetle aggregation pheromone.
- Wenkert, Ernest,Michelotti, Enrique L.,Swindell, Charles S.,Tingoli, Marco
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p. 4894 - 4899
(2007/10/02)
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- STEREOCHEMICAL OBSERVATIONS ON THE WITTIG REACTION OF OXIDO PHOSPHONIUM YLIDES WITH ALDEHYDES
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The reaction of aldehydes with oxido ylides shows a dramatic dependence of alkene stereochemistry on the distance between oxygen and phosphorus atoms; ylides with proximal O and P atoms favor production of E alkenes.The high E stereoselectivity with γ-oxido ylides is not mainly attributable to intramolecular proton-exchange in a Wittig intermediate.
- Maryanoff, Bruce E.,Reitz Allen B.,Duhl-Emswiler, Barbara A.
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p. 2477 - 2480
(2007/10/02)
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- ANOMALOUS STEREOCHEMISTRY IN THE WITTIG REACTION INDUCED BY NUCLEOPHILIC GROUPS IN THE PHOSPHONIUM YLIDE
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Reaction of ylides from 3-9 with benzaldehyde show that carboxylate and oxido functionalities proximate to the ylide center promote anomalously high E stereoselectivity in alkene formation.Through the use of α-deuterated ylides 12-14, an internal "trans-selective Wittig" mechanism was ruled out as a principal source of exaggerated E alkene production.
- Maryanoff, Bruce E.,Duhl-Emswiler, B. A.,Reitz, Allen B.
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p. 187 - 190
(2007/10/02)
-