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A stereospecific synthesis of 2,3-disubstituted tetrahydrofuran derivatives
A stereospecific synthesis of 2,3-difunctionalised tetrahydrofurans via a transmetallation-alkylation sequence of the corresponding 2-(tri-butylstannyl)tetrahydrofurans is described.
Zhao, Yuekun,Beddoes, Roy L.,Quayle, Peter
p. 4183 - 4186
(1994)
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Highly Enantioselective Iridium-Catalyzed Coupling Reaction of Vinyl Azides and Racemic Allylic Carbonates
The iridium-catalyzed enantioselective coupling reaction of vinyl azides and allylic electrophiles is presented and provides access to β-chiral carbonyl derivatives. Vinyl azides are used as acetamide enolate or acetonitrile carbanion surrogates, leading to γ,δ-unsaturated β-substituted amides as well as nitriles with excellent enantiomeric excess. These products are readily transformed into chiral N-containing building blocks and pharmaceuticals. A mechanism is proposed to rationalize the chemoselectivity of this coupling reaction.
Han, Min,Yang, Min,Wu, Rui,Li, Yang,Jia, Tao,Gao, Yuanji,Ni, Hai-Liang,Hu, Ping,Wang, Bi-Qin,Cao, Peng
supporting information
p. 13398 - 13405
(2020/09/02)

Asymmetric Synthesis of γ-Secondary Amino Alcohols via a Borrowing-Hydrogen Cascade
The borrowing-hydrogen (or hydrogen autotransfer) process, where the catalyst dehydrogenates a substrate and formally transfers the H atom to an unsaturated intermediate, is an atom-efficient and environmentally benign transformation. Described here is an example of an asymmetric borrowing-hydrogen cascade for the formal anti-Markovnikov hydroamination of allyl alcohols to synthesize optically enriched γ-secondary amino alcohols. By exploiting the Ru-(S)-iPrPyme catalyst with minimal stereogenicity, a cascade process including dehydrogenation, conjugate addition, and asymmetric reduction was developed. The mild conditions, functional group tolerance, and broad substrate scope (54 examples) demonstrate the synthetic practicality of the catalytic system.
Chang, Xiaoyong,Chen, Fumin,He, Dongxu,Jin, Ming Yu,Pan, Yupeng,Xing, Xiangyou,You, Yipeng
supporting information
p. 7278 - 7283
(2020/10/02)

Tailoring Interfacial Lewis Acid-Basic Pair on ZnO/4Mg1ZrOx Allows Dehydrogenative α-Methylenation of Alcohols with Methanol to Allylic Alcohols
Allylic alcohols are the essential building blocks widely used in diverse streams of organic inventions for pharmaceuticals, fragrances, agrochemicals and polymers. Currently, allylic alcohols are industrially produced from petroleum-based feedstocks via atom uneconomic processes. More sustainable synthesis route for allylic alcohols is limited. Herein, a methodology for the direct and highly selective production of allylic alcohols has been accomplished by controlled dehydrogenative α-methylenation of alcohols with methanol. This transformation is enabled by interfacial Lewis acid-basic pair on tailor-made ZnO/4Mg1ZrOx mixed oxide. High selectivity (83～92%) of allylic alcohols is the consequence of alcohols acceptorless dehydrogenation to liberation of H2 and Meerwein-Ponndorf-Verley type hydrogen transfer onto C = O bonds of unsaturated aldehydes. Furthermore, the prepared ZnO/4Mg1ZrOx mixed oxide shows good stability after 200 h time on stream test. These observations could additionally allow us to design multifunctional solid acid-basic catalysts for the transformations of renewable oxygenates into value-added chemicals.
Fu, Aixiao,Jiang, Shifeng,Liu, Qiang,Liu, Xiaoran,Liu, Xiuyun,Mu, Xindong,Sun, Mengqing,Wang, Xicheng,Xu, Guoqiang,Zhao, Lingling
(2020/10/07)

Access to Saturated Thiocyano-Containing Azaheterocycles via Selenide-Catalyzed Regio-A nd Stereoselective Thiocyanoaminocyclization of Alkenes
An efficient route for the synthesis of saturated thiocyano-containing azaheterocycles by selenide-catalyzed regio-A nd stereoselective thiocyanoaminocyclization of alkenes is disclosed. The desired products were obtained in moderate to high yields under mild conditions. The generality of this method was elucidated by its efficient application in thiocyano oxycyclization of alkenes.
Wei, Wei,Liao, Lihao,Qin, Tian,Zhao, Xiaodan
supporting information
p. 7846 - 7850
(2019/10/10)

Visible light-induced diastereoselective semihydrogenation of alkynes to cis-alkenes over an organically modified titanium(IV) oxide photocatalyst having a metal co-catalyst
Hydrogen (H2)-free and poison (lead and quinoline)-free semihydrogenation of alkynes to cis-alkenes under gentle conditions is one of the challenges to be solved. In this study, a titanium(IV) oxide photocatalyst having two functions (visible light responsiveness and semihydrogenation activity) was prepared by modification with 2,3-dihydroxynaphthalene (DHN) and a copper (Cu) co-catalyst, respectively. The photocatalyst (DHN/TiO2-Cu) showed high performance for diastereoselective semihydrogenation of alkynes to cis-alkenes in water-acetonitrile solution under visible light irradiation without the use of H2 and poisons. Alkynes having reducible functional groups were converted to the corresponding alkenes with the functional groups being preserved. The addition of water to acetonitrile changed the amount of alkynes adsorbed on the photocatalyst, which was a decisive factor determining the rate of hydrogenation. A relatively large apparent activation energy, 27 kJ mol?1, was obtained by a kinetic study, indicating that the rate-determining step of this reaction was not an electron production process but a thermal catalytic semihydrogenation process over the Cu co-catalyst. Semihydrogenation and hydrogen evolution occurred competitively on Cu metals and the former became predominant at slightly elevated temperatures, which is discussed on the basis of the kinetic parameters of two reactions.
Fukui, Makoto,Omori, Yuya,Kitagawa, Shin-ya,Tanaka, Atsuhiro,Hashimoto, Keiji,Kominami, Hiroshi
p. 36 - 42
(2019/05/04)

Stereodivergence in the Ireland-Claisen Rearrangement of α-Alkoxy Esters
A systematic investigation into the Ireland-Claisen rearrangement of α-alkoxy esters is reported. In all cases, the use of KN(SiMe3)2 in toluene gave rearrangement products corresponding to a Z-enolate intermediate with excellent diastereoselectivity, presumably because of chelation control. On the other hand, chelation-controlled enolate formation could be overcome for most substrates through the use of lithium diisopropylamide (LDA) in tetrahydrofuran (THF).
Podunavac, Ma?a,Lacharity, Jacob J.,Jones, Kerry E.,Zakarian, Armen
supporting information
p. 4867 - 4870
(2018/08/24)

Enantioselective addition of selenosulfonates to α,β-unsaturated ketones
An organo-catalyzed enantioselective addition of selenosulfonates to α,β-unsaturated ketones was developed for the first time. With a chiral squaramide as an efficient catalyst, the desired α-selenylated ketones were obtained in a good yields with high enantioselectivity up to 89% ee, and good results could be obtained on a gram scale. The products could also be efficiently transformed into useful building blocks with a propenylic stereocenter; the strategy presented in this study may find further applications in organic synthesis.
Luo, Shilong,Zhang, Nan,Wang, Zhen,Yan, Hailong
supporting information
p. 2893 - 2901
(2018/05/03)

A Re2O7catalyzed cycloetherification of monoallylic diols
A Re2O7catalyzed cycloetherification of monoallylic diols is described. The reaction features short reaction time, mild reaction conditions and exclusive E selectivity. A wide range of monoallylic alcohols with alkyl or aryl substituents on olefin smoothly undergo ring closure to deliver corresponding oxa-heterocycles. The reaction is also operationally simple and not sensitive to air and moisture.
Wan, Xiaolong,Hu, Jiadong,Xu, Dongyang,Shang, Yang,Zhen, Yanxia,Hu, Chenchen,Xiao, Fan,He, Yu-Peng,Lai, Yisheng,Xie, Weiqing
supporting information
p. 1090 - 1093
(2017/03/02)

A short and modular approach towards 3,5-disubstituted indolizidine alkaloids
3,5-Dialkyl indolizidines have been prepared in four linear steps from commercially available starting materials. The sequence involves two direct α-functionalization steps and a subsequent reductive amination and provides diastereoselective access to both C-3 epimers of the 5,9-trans-substituted indolizines. The naturally occurring indolizidines 195B and 223AB have been synthesized using this methodology.
Nebe, Marco M.,Zinn, Sina,Opatz, Till
p. 7084 - 7091
(2016/07/30)

Titanocene(III) chloride mediated radical induced addition-elimination route to the synthesis of racemic and optically active trisubstituted tetrahydrofurans: Formal synthesis of magnofargesin and 7’-epimagnofargesin
Titanocene(III) Chloride mediated radical induced synthesis of 4-benzylidene substituted tetrahydrofuran, a typical lignan skeleton, has been accomplished in good yield through addition-elimination route in racemic as well as in optically active forms. The method has been applied to the synthesis of furano lignans, magnofargesin (1) and 7’-epimagnofargesin (2) in optically active forms.
Chakraborty,Mandal,Roy
p. 1067 - 1079
(2016/07/19)

Organoselenium-catalyzed, hydroxy-controlled regio- and stereoselective amination of terminal alkenes: Efficient synthesis of 3-amino allylic alcohols
An efficient route to prepare 3-amino allylic alcohols in excellent regio- and stereoselectivity in the presence of bases by orangoselenium catalysis has been developed. In the absence of bases α,β-unsaturated aldehydes were formed in up to 97% yield. Control experiments reveal that the hydroxy group is crucial for the direct amination.
Deng, Zhimin,Wei, Jialiang,Liao, Lihao,Huang, Haiyan,Zhao, Xiaodan
supporting information
p. 1834 - 1837
(2015/04/27)

3-Chloro-1-lithiopropene, a functional organolithium reagent, and its reactions with alkylboronates to give 3-alkylprop-1-en-3-ols
The reagent 3-chloro-1-lithiopropene (4) can be generated by treating 1-bromo-3-chloropropene with t-BuLi. It is unstable but if generated at low temperature in the presence of alkylboronic esters, such as 3, is trapped in situ to give rearrangement products 2, which on oxidation give 3-alkylprop-1-en-3-ols in good yields. The reaction works for primary, secondary, benzylic, and even tertiary alkylboronic esters, providing allylic alcohols bearing almost any alkyl group available using organoborane chemistry and incorporating all features of such groups.
Smith, Keith,Elliott, Mark C.,Jones, D. Heulyn
p. 9526 - 9531
(2013/10/08)

Stereoselective synthesis of umuravumbolide
An efficient stereoselective total synthesis of umuravumbolide has been developed. The key features of the synthesis include Jacobsen resolution, Wadsworth Emmons olefination and silyl-tethered ring closing metathesis.
Kumar, T. Vijaya,Reddy, G. Venkateswar,Babu, K. Suresh,Rao, J. Madhusudana
p. 594 - 598
(2013/06/27)

Stereoselective synthesis of pectinolide C
The first total synthesis of the pectinolide C has been accomplished using the silyl-tethered ring closing metathesis, Jacobsen resolution, and Wadsworth-Emmons olefinations as key reaction sequences. Copyright
Kumar, T. Vijaya,Shankaraiah,Babu, K. Suresh,Rao, J. Madhusudana
p. 1397 - 1400
(2013/04/10)

Total synthesis of umuravumbolide and hyptolide through silicon-tethered ring-closing metathesis
The total synthesis of umuravumbolide and hyptolide has been achieved in a efficient manner by using temporary silicon-tethered ring-closing metathesis and cross-coupling reactions as key steps. The stereogenic centres were generated by means of proline-catalysed α-aminoxylation of aldehydes and Brown's asymmetric allylation method. An efficient total synthesis of umuravumbolide and hyptolide has been achieved by using temporary silicon-tethered ring-closing metathesis. The stereogenic centres were generated by using asymmetric allyl boration and proline-catalysed α-aminoxylation with high degrees of enantioselectivity. Copyright
Chowdhury, Partha Sarathi,Kumar, Pradeep
p. 4586 - 4593
(2013/07/26)

Enantioselective synthesis of isotopically labeled homocitric acid lactone
A concise synthesis of homocitric acid lactone was developed to accommodate systematic placement of carbon isotopes (specifically 13C) for detailed studies of this cofactor. This new route uses a chiral allylic alcohol, available in multigram quantities from enzymatic resolution, as a starting material, which transposes asymmetry through an Ireland-Claisen rearrangement.
Moore, Jared T.,Hanhan, Nadine V.,Mahoney, Maximillian E.,Cramer, Stephen P.,Shaw, Jared T.
supporting information
p. 5615 - 5617
(2013/12/04)

Catalytic enantioselective addition of alkyl grignard reagents to aliphatic aldehydes
Herein, we report an efficient catalytic system for the enantioselective addition of alkyl Grignard reagents to a broad range of aliphatic aldehydes with good yields and enantioselectivities. Remarkably, the challenging methylmagnesium bromide (MeMgBr) can also be added to a variety of aliphatic aldehydes, providing versatile chiral methyl carbinol units with unprecedented yields and enantioselectivities in a simple one-pot procedure under mild conditions. Copyright
Fernandez-Mateos, Emilio,Macia, Beatriz,Yus, Miguel
supporting information
p. 1249 - 1254
(2013/06/27)

The synthesis of long-chain α-alkyl-β-hydroxy esters using allylic halides in a Frater-Seebach alkylation
The Frater-Seebach alkylation is a highly efficient means to diastereoselectively introduce α-substituents to chiral β-hydroxy esters, however, the yields of reactions in which longer chain alkyl halides are used can be disappointing. To provide a more robust protocol for the alkylation of β-hydroxy esters, we prepared a variety of long-chain allylic iodides with the view that the greater reactivity of the allylic system would lead to enhanced efficiency. Indeed, for all substrates studied, the yield of the α-alkylation was greatly improved for the unsaturated allylic halides compared to their analogous saturated counterparts. Our methodology thus provides an improved means by which to access a variety of important lipophilic compounds such as mycolic acids, which are found on the cell wall of M. tuberculosis. An improved methodology for the introduction of α-substituents to chiral β-hydroxy esters using Frater-Seebach methodology is presented. Long-chain allylic iodides resulted in better yields for the α-alkylation compared to their saturated counterparts. This methodology provides an improved means by which to access a variety of important lipophilic compounds such as mycolic acids. Copyright
Khan, Ashna A.,Chee, Stephanie H.,Stocker, Bridget L.,Timmer, Mattie S. M.
supporting information; experimental part
p. 995 - 1002
(2012/03/27)

The substrate spectrum of the inverting sec-alkylsulfatase Pisa1
The substrate spectrum of the inverting alkylsulfatase Pisa1 was investigated using a range of sec-alkyl sulfate esters bearing aromatic, olefinic and acetylenic moieties. Perfect enantioselectivities were obtained for substrates bearing groups of different size adjacent to the sulfate ester moiety. Insufficient selectivities could be doubled by using dimethyl sulfoxide (DMSO) as co-solvent. Hydrolytically unstable benzylic sulfate esters could be sufficiently stabilised by introduction of electron-withdrawing substituents. Overall, Pisa1 appears to be a very useful inverting alkylsulfatase for the deracemisation of rac-sec-alcohols via enzymatic hydrolysis of their corresponding sulfate esters, which furnishes homochiral products possessing the 'anti-Kazlauskas' configuration. Copyright
Schober, Markus,Knaus, Tanja,Toesch, Michael,MacHeroux, Peter,Wagner, Ulrike,Faber, Kurt
p. 1737 - 1742
(2012/07/31)

Catalytic ring expansion of vinyl oxetanes: Asymmetric synthesis of dihydropyrans using chiral counterion catalysis
Acid Showdown! The first catalytic ring expansion of vinyl oxetanes to 3,6-dihydro-2H-pyrans is described. Copper(II) triflate emerged as the best catalyst for this new transformation, which has broad scope as demonstrated by the eighteen examples included. The symmetric vinyl oxetane substrate can be asymmetrically desymmetrized when using either chiral Lewis or Bronsted acids as catalysts. Copyright
Guo, Boying,Schwarzwalder, Gregg,Njardarson, Jon T.
p. 5675 - 5678
(2012/07/03)

L-Proline-derived ligands to mimic the '2-His-1-carboxylate' triad of the non-haem iron oxidase active site
Non-haem iron(II) oxidases (NHIOs) catalyse a variety of oxidative transformations in biology. The iron-binding environment of the NHIO active site typically incorporates a '2-His-1-carboxylate' facial triad of amino acid side-chains, a motif that has emerged as a defining feature of the enzyme family. Towards the goal of biomimetic, iron-mediated C-H activation we have synthesized a series of peptidomimetic ligands from l-proline. By coupling l-proline to 2,6-bis(bromomethyl)pyridine, 2-(bromomethyl)-6-((tert- butyldimethylsilyloxy)methyl)pyridine and picolinic acid, we have generated several new ligand architectures designed to complex with iron(II) and mimic the NHIO active site. The resulting iron complexes promote modest levels of alkene dihydroxylation and allylic oxidation using hydrogen peroxide as oxidant.
Dungan, Victoria J.,Wong, Shwo Mun,Barry, Sarah M.,Rutledge, Peter J.
experimental part
p. 3231 - 3236
(2012/06/01)

Highly regioselective control of 1,2-addition of organolithiums to α,β-unsaturated compounds promoted by lithium bromide in 2-methyltetrahydrofuran: A facile and eco-friendly access to allylic alcohols and amines
Very high regioselective 1,2-addition of organolithiums to α,α-unsaturated carbonyl-like compounds (ketones, aldehydes, and imines) in the presence of LiBr was achieved by carrying out reactions in the sustainable solvent 2-methyltetrahydrofuran. Excellent yields (in isolated product) of allylic alcohols and allylic amines were recovered under a simple experimental procedure at 0 °C.
Pace, Vittorio,Castoldi, Laura,Hoyos, Pilar,Sinisterra, José Vicente,Pregnolato, Massimo,Sánchez-Montero, Ma. José
supporting information; experimental part
p. 2670 - 2675
(2011/04/23)

α-Aroyloxyaldehydes: Scope and limitations as alternatives to α-haloaldehydes for NHC-catalysed redox transformations
α-Aroyloxyaldehydes are readily prepared bench stable synthetic intermediates. Their ability to act as α-haloaldehyde surrogates for NHC-promoted redox esterifications and in [4+2] cycloadditions is described.
Ling, Kenneth B.,Smith, Andrew D.
supporting information; experimental part
p. 373 - 375
(2011/02/24)

Pentanidium-catalyzed enantioselective phase-transfer conjugate addition reactions
A new chiral entity, pentanidium, has been shown to be an excellent chiral phase-transfer catalyst. The enantioselective Michael addition reactions of tert-butyl glycinate-benzophenone Schiff base with various α,β- unsaturated acceptors provide adducts with high enantioselectivities. A successful gram-scale experiment at a low catalyst loading of 0.05 mol % indicates the potential for practical applications of this methodology. Phosphoglycine ester analogues can also be utilized as the Michael donor, affording enantioenriched α-aminophosphonic acid derivatives and phosphonic analogues of (S)-proline.
Ma, Ting,Fu, Xiao,Kee, Choon Wee,Zong, Lili,Pan, Yuanhang,Huang, Kuo-Wei,Tan, Choon-Hong
supporting information; experimental part
p. 2828 - 2831
(2011/04/22)

First example of hydrolytic kinetic resolution of acrylate of secondary alcohols by lipase Amano AK
Lipase Amano AK is found to be extremely efficient catalyst for hydrolytic kinetic resolution of acrylates of secondary alcohols in aqueous phosphate buffer at pH 7.0. Both aliphatic and benzylic secondary alcohols show good to excellent E values.
Bora, Pranjal P.,Bez, Ghanashyam,Anal, Jasha Momo H.
experimental part
p. 270 - 275
(2012/07/03)

Olefin epoxidation with tert-BuOOH catalyzed by vanadium polyoxometalate immobilized on ionic liquid-modified MCM-41
Preparation and characterization of vanadium-containing polyphosphomolybdates supported on ionic liquid-modified MCM-41, MCM-41-Im, are reported. The catalyst, [PVMo@MCM- 41-Im], was characterized by elemental analysis, X-ray diffraction, scanning electron microscopy and also FT-IR, and UV-Vis spectroscopic methods. This heterogeneous catalytic system was applied for efficient epoxidation of various olefins in the presence of tert-BuOOH in 1,2-dichloroethane under reflux. The catalyst can be reused several times without apparent loss of its catalytic performance.
Hajian, Robabeh,Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Khosropour, Ahmad Reza
scheme or table
p. 4134 - 4144
(2012/03/26)

Syntheses of aggregation pheromones of the palm weevils rhyncophorus vulneratus and rphoenicis and of (+)- trans-whiskey lactone
(3S,4S)-3-Methyloctan-4-ol, (4S,5S)-4-methylnonan-5-ol, and (+)-trans-whiskey lactone [(4S,5R)-5-butyl-4-methyldihydrofuran-2(3H)-one] were synthesized stereoselectively by using a radical cyclization reaction as a key step. All three molecules were synthesized from a common cyclic acetal intermediate. Georg Thieme Verlag Stuttgart. New York.
Yadav,Rao, C. Venkateshwar,Prasad,Khazim Al Ghamdi, Ahmad Al
p. 3894 - 3898
(2012/01/06)

Diastereotopos-differentiating allylic alkylation as a key step in the synthesis of γ-glutamyl boletine
A straightforward approach towards γ-glutamyl boletine is described, based on a diastereotopos-differentiating allylic alkylation of chelated amino acid ester enolates. Independent of the configuration of the leaving group in the allylic substrate, the allylation product is obtained as a single stereoisomer. Its configuration is solely controlled by the stereogenic center adjacent to the π-allyl complex formed.
Gawas, Dnyaneshwar,Kazmaier, Uli
experimental part
p. 457 - 462
(2010/02/15)

Chiral a-substituted allylboronates in a one-pot three-component asymmetric allylic alkylation/carbonyl allylation reaction sequence -Applications to the syntheses of (+)-(3R,5R)-3-hydroxy-5-decanolide and (-)-massoialactone
The use of different organomagnesium reagents in the copper-catalyzed allylic alkylation of 3-chloropropenyl with chiral phosphoramidite ligands produces the desired a-substituted allylic boronate reagents in high and with modest to high enantioselectivities (up to 96% ee). The size of the incoming alkyl substituent the organomagnesium reagent was found to impact the yield and selectivity of the allylic alkylation. A one-pot for the preparation of these chiral allylic boronates followed by a Lewis acid (BF3) catalyzed addition to aldehydes the desired allylboration products, homoallylic secondary alcohols, in good yields and very high diastereoselectivity.three-component reaction methodology was applied to the syntheses of two lactone-containing natural , (-)-massoialactone and (+)-(3R,5R)-3-hydroxy-5-decanolide. The key step of these syntheses involved the pot enantioselective copper-catalyzed allylic alkylation/allylboration reaction with a benzylic aldehyde, and the desired product in 87% yield, 92% e,and high E/Z selectivity in a ratio of 22:1. Remarkably, the alkylation step of this sequential reaction was performed with a low catalyst loading of 2 mol% on a scale >15 mmol that can provide multiple grams of the three-component product.
Carosi, Lisa,Hall, Dennis G.
experimental part
p. 650 - 661
(2009/10/30)

A general and highly selective chelate-controlled intermolecular oxidative heck reaction
A novel chelate-controlled intermolecular oxidative Heck reaction is reported that proceeds with a wide range of nonresonance stabilized α-olefin substrates and organoboron reagents to afford internal olefin products in good yields and outstanding regio- and E:Z stereoselectivities. Pd-H isomerization, common in many Heck reactions, is not observed under these mild, oxidative conditions. This is evidenced by outstanding E:Z selectivities (>20:1 in all cases examined), no erosion in optical purity for proximal stereogenic centers, and a tolerance for unprotected alcohols. Remarkably, a single metal/ligand combination, Pd/bis-sulfoxide complex 1, catalyzes this reaction over a broad range of coupling partners. Given the high selectivities and broad scope, we anticipate this intermolecular Heck reaction will find heightened use in complex molecule synthesis. Copyright
Delcamp, Jared H.,Brucks, Alexandria P.,White, M. Christina
supporting information; scheme or table
p. 11270 - 11271
(2009/02/05)

Kinetic resolution of racemic secondary aliphatic allylic alcohols in lipase-catalyzed transesterification
Different lipases were screened as biocatalysts in the kinetic resolution process of (±)-hept-1-en-3-ol 1, (±)-5-methylhex-1-en-3-ol 2, (±)-6-methylhept-2-en-4-ol 3, (±)-6,6-dimethylhept-2-en-4-ol 4, and 1-phenylbut-3-en-2-ol 5 by enantioselective transesterification. The acylation of (±)-1 and (±)-2 catalyzed by Novozym 435 (Candida antarctica) was very effective and proceeded with good enantioselectivity. After 4-8 h of reactions the esters formed and the alcohols, which remained were obtained with high enantiomeric excess with 97-100% ee and 91-100% ee, respectively. The lipase Amano PS (Burkholderia cepacia) was the best catalyst in the asymmetric transesterification of (±)-5 affording the (R)-alcohol with 90-95% ee and the (S)-ester with 98-100% ee. Low enantioselectivities were observed in the cases of lipase-catalyzed acylation of (±)-3 and (±)-4.
Chojnacka, Anna,Obara, Robert,Wawrzenczyk, Czeslaw
p. 101 - 107
(2007/10/03)

Atom transfer radical cyclization (ATRC) applied to a chemoenzymatic synthesis of Quercus lactones
The natural fragrances (+)-trans whisky lactone 2 and (+)-trans cognac lactone 4, together with a minor amount of their (-)-cis stereoisomers, were prepared in 50% and 42% overall yield, respectively, starting from racemic 1-hepten-3-ol (±)-5 and 1-octen-3-ol (±)-6. The procedure involved first the enantioconvergent, lipase mediated transformation of the secondary allylic alcohols derived dichloroacetates (±)-7 and (±)-8 into the corresponding homochiral (+)-7 and (+)-8, combined with their cyclization under a transition metal catalyzed atom transfer process.
Felluga, Fulvia,Forzato, Cristina,Ghelfi, Franco,Nitti, Patrizia,Pitacco, Giuliana,Pagnoni, Ugo Maria,Roncaglia, Fabrizio
p. 527 - 536
(2007/10/03)

Chemoenzymatic synthesis of optically active γ-alkyl-γ-butenolides
rac-Hept-1-en-3-ol 4 was subjected to an enantioselective esterification in the presence of Novozyme 435 and vinyl crotonate as the acyl donor to give (3S)-oct-1-en-3-yl crotonate 7 in >99% ee and (3R)-alcohol 4 in 99% ee. The E-value of this enzymatic reaction was found to be >1000. The (S)-crotonic ester 7 was converted by ring-closing metathesis (RCM) using Grubbs' catalyst to give (S)-oct-2-en-4-olide 1 in 96% yield while keeping the high enantiomeric excess.
Fujii, Mikio,Fukumura, Motonori,Hori, Yumiko,Hirai, Yasuaki,Akita, Hiroyuki,Nakamura, Kaoru,Toriizuka, Kazuo,Ida, Yoshiteru
p. 2292 - 2298
(2007/10/03)

A chiral electrophilic selenium reagent to promote the kinetic resolution of racemic allylic alcohols
(Chemical Equation Presented) The first example of a kinetic resolution process promoted by electrophilic selenium reagents is reported. Racemic allylic alcohols react with half equivalents of a selenenylating agent in methanol leading to the regiospecific formation of the corresponding addition products with a very high level of facial selectivity (from 95:5 to 98:2 dr). The unreacted alcohols can be recovered in an optically enriched form (from 90 to 94% ee).
Tiecco, Marcello,Testaferri, Lorenzo,Santi, Claudio,Tomassini, Cristina,Bonini, Rosaria,Marini, Francesca,Bagnoli, Luana,Temperini, Andrea
p. 4751 - 4753
(2007/10/03)

The regioselective 1,4-addition reaction of alkenylboronic acids to α,β,α′,β′-unsaturated ketones
The effect of substituents on the double bond of α,β-unsaturated ketones for the 1,4-addition reaction rate of alkenylboronic acids induced by cyanuric fluoride was studied in detail. When the steric hindrance around the β-carbon of the unsaturated ketones increased, the 1,4-addition reaction rate significantly decreased. An alkyl substituent on the α-carbon was also found to significantly affect the 1,4-addition reaction. From these results, unsymmetric α,β,α′,β′unsaturated ketones (10a-f) were designed for the regioselective 1,4-addition reaction with alkenylboronic acids (4a-j). Since they have substituents to disturb the 1,4-addition reaction on only one double bond, the alkenylboronic acids reacted with them from only one side to selectively provide γ,δ,α′,β′-unsaturated ketones (11a-q). Further transformations of the resulting γ,δ,α′,β′-unsaturated ketones were also performed.
Hara, Shoji,Shudoh, Hisashi,Ishimura, Shigeyuki,Suzuki, Akira
p. 2403 - 2408
(2007/10/03)

Tellurium in the 'no-solvent' organic synthesis of allylic alcohols
Elemental tellurium can be reduced by rongalite (HOCH2SO2Na·2H2O)-KOH in the solid phase by application of ultrasound or by microwave irradiation. Without solvent, the organic substrate leg sulfonate ester of an oxiranemethanol) is added with further sonication or irradiation to yield the desired organic product leg allylic alcohols) and elemental Te which may be recycled Phase-transfer conditions (water-toluene) also are satisfactory.
Xu, Qinyu,Chao, Bin,Wang, Yongmei,Dittmer, Donald C.
p. 12131 - 12146
(2007/10/03)

Asymmetric dihydroxylation of allylic phosphine oxides
Diphenylphosphinoyl diols have been produced by asymmetric dihydroxylation (AD) of allylic phosphine oxides and have been shown to be useful synthetic intermediates. The results of this study are discussed in terms of the model which has been proposed by Sharpless to explain the enantioselectivity of his AD reaction. The dihydroxylation results are thus of both mechanistic and synthetic value.
Nelson, Adam,Warren, Stuart
p. 2645 - 2657
(2007/10/03)

Simple one-pot transformations of toluene-p-sulfonates of 2,3-epoxy alcohols into allylic alcohols
A simple synthetic method for the preparation of scalemic allylic alcohols from toluene-p-sulfonates of scalemic 2,3-epoxy alcohols is reported. Satisfactory yields are obtained by treatment of toluene-p-sulfonates of 2,3-epoxy alcohols with potassium iodide followed by triphenylphosphine and iodine in a one-pot synthesis.
Fujii, Nobutaka,Habashita, Hiromu,Akaji, Masako,Nakai, Kazuo,Ibuka, Toshiro,Fujiwara, Masahiro,Tamamura, Hirokazu,Yamamoto, Yoshinori
p. 865 - 866
(2007/10/03)

Concentration effects in chelation controlled reactions
The diastereoselectivities of addition reactions of allyltrimethylsilane to an α-benzyloxyaldehyde were found to be relatively insensitive to the amount of added TiCl4, and to the absolute concentration of the 1:1 aldehyde/TiCl4 complex. In contrast, diastereoselectivities of similar additions to a structurally related β-benzyloxyaldehyde were highly dependent on these variables.
Springer,Springer, James B.,DeBoard,Deboard, Julie,Corcoran,Corcoran, Robert C.
p. 8733 - 8736
(2007/10/02)

Highly Diastereoselective Synthesis of Substituted Epichlorohydrins and Regioselective Preparation of Allyl Alcohols using Chloro or Idomethyllithium
Substituted epichlorohydrins 3 or 6 are obtained α-bromo or α-chlorocarbonyl compounds (1 or 4) and chloro or iodomethyllithium, respectively.Starting from α-bromocarbonyl compounds 1 or acyclic α-chloro ketones the reaction takes place with total diastereoselectivity.Treatment of epichlorohydrins 3 or 6 with lithium iodide affords the same substituted allyl alcohols 7 in a regioselective manner.A mechanism to explain this transformation is proposed.Regioisomeric allyl alcohols 11 are prepared by reaction of epichlorohydrins 6 with lithium powder.
Concellon, Jose M.,Llavona, Lujan,Bernad, Pablo L. Jr.
p. 5573 - 5584
(2007/10/02)

Synthesis of Optically Active 1,2-Epoxy-3-ols
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Heravi, M. M.
p. 349 - 354
(2007/10/03)

New Alkaloids from Ants: Identification and Synthesis of (3R,5S,9R)-3-Butyl-5-(1-oxopropyl)indolizidine and (3R,5R,9R)-3-Butyl-5-(1-oxopropyl)indolizidine Constituents of the Poison Gland Secretion in Myrmicaria eumenoides (Hymenoptera Formicidae)
The (3R,5S,9R) and (3R,5R,9R) stereoisomers of 3-butyl-5-(1-oxopropyl)indolizidine (9) were identified as major constituents of the poison gland secretion of the African ant, Myrmicaria eumenoides.Racemates of the four diastereomers of 9 were synthesized via the corresponding ethyl 5-(5-butylpyrrolidin-2-yl)pentanoates (6).Enantiomerically pure samples of the (3R)-stereoisomers of 9 were obtained by starting from (2R)-2,3-O-isopropylideneglyceric aldehyde (21) and 6-methylpyridine-2-carboxaldehyde (20).In addition, the enantiomeric separation by chiral gas chromatography and unambiguous structure assignment of the target compounds are described. - Key Words: Ants/ Alkaloids/ Myrmicaria eumenoides/ 3-Butyl-5-(1-oxopropyl)indolizidine, (3R,5S,9R)-, (3R,5R,9R)-
Francke, Wittko,Schroeder, Frank,Walter, Felix,Sinnwell, Volker,Baumann, Horst,Kaib, Manfred
p. 965 - 978
(2007/10/02)

A study of methyl and tert-butyl as non migrating groups in the reaction of me(organyl)zinc and t-bu(organyl)zinc with aldehydes
A series of mixed methyl (organyl) and tert-butyl(organyl)zincs were prepared by reaction of ZnCl2 with Grignard reagents. In the presence of salts t-butyl migrates to a lessor extent than methyl in the reaction with aldehydes. In the absence of salts both groups are comparable. BuZnMe prepared under salt-free conditions adds to benzaldehyde in 82.4% ee and in 85% yield, comparable to the reaction with distilled dibutylzinc.
Laloe, Eric,Srebnik, Morris
p. 5587 - 5590
(2007/10/02)

Synthesis of 4-methoxy-N-{2-[3-(methylamino)phenyl}benzamide, and antiarrhythmic compound related to encainide
A ring-opened side product 3, formed during the reduction of a pyridinium precursor to the antiarrhythmic drug, encainide (2), was isolated. The structure of 3 was confirmed by an independent synthesis from o-iodonitrobenzene and 1-hepten-3-ol. The key step was a palladium(II) catalyzed coupling to introduce the 3-oxoheptyl side chain onto the aromatic ring. Synthetic 3 exhibited significant antiarrhythmic activity.
Thompson,Torabi
p. 965 - 968
(2007/10/02)

Novel Conversion of Epoxides to One Carbon Homologated Allylic Alcohols by Dimethylsulfonium Methylide
The reaction of excess of dimethylsulfonium methylide with terminal, allylic, or benzylic epoxides affords good to excellent yields of one carbon homologated allylic alcohols.
Alcaraz, L.,Harnett, J. J.,Mioskowski, C.,Martel, J. P.,Gall, T. Le,et al.
p. 5449 - 5452
(2007/10/02)

Preparation of disubstituted epichlorohydrins with total diastereoselectivity. Transformation of α-bromocarbonyl compounds into allyl alcohols
Epichlorohydrins 3 have been obtained with total diastereoselectivity from α-bromocarbonyl compounds and chloromethyllithium generated in situ. The treatment of compounds 3 with lithium iodide or lithium powder affords allyl alcohols 4 in a regioselective manner.
Barluenga, Jose,Llavona, Lujan,Bernad, Pablo L.,Concellon, Jose M.
p. 3173 - 3176
(2007/10/02)

Influence on Insecticidal Activity of the 3-(3,4-Methylenedioxyphenyl) Group in the 1,4-Benzodioxanyl Moiety of Haedoxan
The influence on the insecticidal activity of haedoxan A of its 3-(3,4-methylenedioxyphenyl) group in the 1,4-benzodioxanyl moiety was examined with two (+/-)-(1S*,2R*,5R*,6S*)-6--2-(2,6-dimethoxyphenoxy)-1-hydroxy-3,7-dioxabicyclooctanes.Replacement of the methylenedioxyphenyl group of haedoxan by methyl and n-butyl group resulted in a large decrease in the activity, indicating the importance of the 3-aryl group for the potent insecticidal activity of haedoxan.
Yamauchi, Satoshi,Taniguchi, Eiji
p. 1744 - 1750
(2007/10/02)

PREPARATION OF ALLYL ALCOHOLS FROM MONOHALO- AND GEM-DIHALOBUTYLCYCLOPROPANES IN THE PRESENCE OF COPPER AND ITS SALTS
The reaction of gem-dibromo- or gem-dichlorobutylcyclopropanes with an equimolar amount of CuSO4*5H2O in a mixture of DMSO and water is accompanied by scission of the three-membered ring and formation of the corresponding 2-bromo- or 2-chloroallyl alcohols.The corresponding allyl alcohols were prepared analogously from monobromo- or monochlorocyclopropanes.
Korneva, O. S.,Nefedov, O. M.
p. 2194 - 2196
(2007/10/02)

C-Centered Optically Active Organosilanes. A Rational Approach to an Efficient Silylated Chiral Auxiliary
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Nativi, Cristina,Ravida, Nunziatino,Ricci, Alfredo,Seconi, Giancarlo,Taddei, Maurizio
p. 1951 - 1955
(2007/10/02)