Intramolecular carbolithiation cascades as a route to a highly strained carbocyclic framework: competition between 5-exo-trig ring closure and proton transfer

• William F. Bailey and
• Justin D. Fair

Beilstein J. Org. Chem. 2013, 9, 537–543, doi:10.3762/bjoc.9.59

• reaction appears to provide an interesting … procedure for formation of five-membered ring systems which is potentially significant for synthetic purposes” [3]. Indeed, the facile cyclization of olefinic and acetylenic organolithiums has proven to be a regiospecific and highly stereoselective route [4] to

Development of peptidomimetic ligands of Pro-Leu-Gly-NH₂ as allosteric modulators of the dopamine D₂ receptor

• Swapna Bhagwanth,
• Ram K. Mishra and
• Rodney L. Johnson

Beilstein J. Org. Chem. 2013, 9, 204–214, doi:10.3762/bjoc.9.24

• ) oxidative cleavage of the double bond with OsO4/NaIO4, and (3) hydrogenolysis of the benzyl ester [36][48]. Although the Seebach methodology provides a highly stereoselective way to α-alkylated prolines, there are several shortcomings to the originally developed protocols [47]. In the oxazolidinone

Highly stereocontrolled synthesis of trans-enediynes via carbocupration of fluoroalkylated diynes

• Tsutomu Konno,
• Misato Kishi and
• Takashi Ishihara

Beilstein J. Org. Chem. 2012, 8, 2207–2213, doi:10.3762/bjoc.8.249

• ; carbometallation; diyne; enediyne; fluorine; highly regioselective; highly stereoselective; Introduction trans-Enediynes (trans-hex-3-ene-1,5-diynes), as shown in Figure 1, are well-recognized as one of the most important building blocks because they are frequently utilized for the synthesis of π-conjugated

Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

• Pankaj Chauhan and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2012, 8, 2132–2141, doi:10.3762/bjoc.8.240

• nitrogen activates and orients the dicarbonyl compounds to provide the Michael adduct in high enantioselectivity. Application of grinding with pestle and mortar for highly stereoselective Michael addition of trisubstituted β-ketoesters to nitroalkene derivatives was reported by Chimni’s group (Scheme 8

Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

• Vadim A. Soloshonok,
• José Luis Aceña,
• Hisanori Ueki and
• Jianlin Han

Beilstein J. Org. Chem. 2012, 8, 1920–1928, doi:10.3762/bjoc.8.223

• corresponding Ni(II) complexes, the formation of quasi-diastereomeric products is highly stereoselective providing formation of only two, (Ra*,Mh*,Rc*) and (Ra*,Ph*,Rc*), out of the four possible stereochemical combinations. The reversible quasi-diastereomeric transformation between the products (Ra*,Mh*,Rc

• that only two out of the four possible diastereomeric complexes were accessed in a highly stereoselective manner, as a result of the intrinsic steric hindrance associated with the design of achiral ligands 1. In addition, crystallization of the diastereomeric mixtures resulted in the formation of a

Facile synthesis of functionalized tetrahydroquinolines via domino Povarov reactions of arylamines, methyl propiolate and aromatic aldehydes

• Jing Sun,
• Hong Gao,
• Qun Wu and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2012, 8, 1839–1843, doi:10.3762/bjoc.8.211

• structure we could conclude that the prepared tetrahydroquinolines 1a–1m exist in (2,3)-trans-(3,4)-trans-configuration, which also means that this domino Povarov reaction is a highly stereoselective reaction. A reaction mechanism for this domino Povarov reaction is briefly outlined in Scheme 2 based on the

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• ]. Similar results of highly stereoselective hydroborations of structurally related chiral cyclopentene derivatives have been reported [20][21]. Synthesis of trans,trans-dihydronepetalactone b To install a trans,trans-configuration between the substituents at C5-C1 and C1-C2 of the cyclopentane backbone

• between 4a-H and 7-CH3 as well as between 4-CH3 and 7a-H, and furthermore, between 4-CH3 and 5-Ha as well as between 5-Ha and 7a-H. Synthesis of a mixture of trans-fused dihydronepetalactones c and d The stereogenic center at C1’ of the acetate 26 keeps (R)-configuration which resulted from highly

• stereoselective hydroboration of the acetate 20 to yield the key intermediate 16 as shown above (Scheme 2). For the synthesis of the cis,trans-dihydronepetalactone d, this stereocenter needed to be isomerized to keep the (4S)-configuration in the final product (Scheme 5). To achieve the required inversion, the

Stereoselective, nitro-Mannich/lactamisation cascades for the direct synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles

• Pavol Jakubec,
• Dane M. Cockfield,
• Madeleine Helliwell,
• James Raftery and
• Darren J. Dixon

Beilstein J. Org. Chem. 2012, 8, 567–578, doi:10.3762/bjoc.8.64

• -component coupling reaction (Scheme 8). As described in our previous communication [61], the employment of bifunctional catalyst 9 [54][55] in a highly stereoselective two-stage one-pot cascade led to the formation of enantiomerically highly enriched spirocycle (+)-1a (Scheme 8). In a repeat of the process

N-Heterocyclic carbene/Brønsted acid cooperative catalysis as a powerful tool in organic synthesis

• Rob De Vreese and
• Matthias D’hooghe

Beilstein J. Org. Chem. 2012, 8, 398–402, doi:10.3762/bjoc.8.43

• ” reactions of aldehydes started as long ago as 1832, and the preparation of sterically hindered triazolium salts in 1996 provided a solid basis for highly stereoselective “umpolung” reactions utilizing NHCs [12]. In addition, conjugate “umpolung” relates to a process in which α,β-unsaturated aldehydes 3 are

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• external vinyl ether 4, leading to interesting 9-oxabicyclo[3.3.1]nona-4,7-dienes 5 in good yields (Scheme 2). In view of the highly stereoselective outcome of these reactions and the requirement of an alkoxy or acyloxy group at the propargylic position of 3, the authors proposed a reaction pathway based

• highly stereoselective (4 + 2) cycloaddition with the vinyl ether to yield, after the elimination of the gold catalyst, highly substituted oxacyclic systems 7 in good yields and with notable diastereoselectivities. Importantly, this reaction tolerates a wide range of vinyl ethers, and different

• intermediate gold carbenoids of type XXIII’, resulting from 1,2-acyloxy migration on propargyl esters such as 31 (pivalates, acetates or benzoates), with external alkenes. Usually, the reactions are highly stereoselective, predominantly affording the cis-cyclopropanic adduct 32. Moreover, the reaction

Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene

• Alexandre Pradal,
• Chung-Meng Chao,
• Patrick Y. Toullec and
• Véronique Michelet

Beilstein J. Org. Chem. 2011, 7, 1021–1029, doi:10.3762/bjoc.7.116

• cycloisomerization process was found to be highly stereoselective in the case of oxygen-tethered enynes (Table 2, entries 6–12). In all cases, the ee’s were greater than 90% and in one case as high as 98%. The stability of the resulting bicyclic alkenes 4 was generally only moderate, which led to low isolated yields

• evaluated: The corresponding bicyclic adducts 4e and 4f were isolated in modest to good yield and 95% ee. Considering the observed highly stereoselective reactions of oxygen-tethered 1,6-enynes, we decided to study the challenging asymmetric synthesis of pentasubstituted cyclopropyl derivatives [67][68][69

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• rearrangement followed by nucleophilic attack of the Boc-protected nitrogen atom. A similar method to synthesize the 2-vinylpiperidin-3-ol 158 by a highly stereoselective gold-catalyzed allene cyclization has been reported (Scheme 27) [72]. The ring expansion of cyclopropane derivatives provides a powerful

• bond. Liu et al. has developed two highly stereoselective cationic gold(I)-catalyzed tandem cyclization reactions of alkynylindoles 322 [160]. The reaction proceeds with remarkable retention of chirality and allows the efficient enantioselective synthesis of polycyclic indolines 327 from the

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• [70] to prepare 5-des(hydroxymethyl)-1-deoxynojirimycin (114) and its mannose analogue 111 (as HCl salts) in a highly stereoselective mode starting from a different common olefin, 107 (Scheme 20). In this case, RCM was promoted by the 2nd-generation Grubbs catalyst 5 which ensured a high yield of the

An efficient and practical entry to 2-amido-dienes and 3-amido-trienes from allenamides through stereoselective 1,3-hydrogen shifts

• Ryuji Hayashi,
• John B. Feltenberger,
• Andrew G. Lohse,
• Mary C. Walton and
• Richard P. Hsung

Beilstein J. Org. Chem. 2011, 7, 410–420, doi:10.3762/bjoc.7.53

• -hydrogen shifts from allenamides are described. These 1,3-hydrogen shifts could be achieved thermally or they could be promoted by the use of Brønsted acids. Under either condition, these processes are highly regioselective in favour of the α-position, and highly stereoselective in favour of the E

• Information File 3) of a single crystal of 2-amido-diene 10b was successfully obtained to assign unambiguously the E-configuration (Figure 1). Encouraged by this highly stereoselective isomerization, we turned our attention to the possibility of constructing synthetically much more challenging 3-amido-trienes

• α-position, and highly stereoselective in favour of the E-configuration. Additionally, 6π-electron electrocyclic ring-closure could be carried out from 3-amido-trienes to afford cyclic 2-amido-dienes, and such electrocyclic ring-closure could be rendered in tandem with the 1,3-hydrogen shift

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• formation reactions in synthetic organic chemistry have attracted considerable attention in recent years [1]. Palladium-catalyzed allylation is also a particularly useful method for the activation of allylic substrates [2]. Trost et al. described a highly stereoselective synthesis of oxazolidinone 2

Stereoselective synthesis of four possible isomers of streptopyrrolidine

• Debendra K. Mohapatra,
• Barla Thirupathi,
• Pragna P. Das and
• Jhillu S. Yadav

Beilstein J. Org. Chem. 2011, 7, 34–39, doi:10.3762/bjoc.7.6

• )-streptopyrrolidine (2) (4R,5S)-streptopyrrolidine (3) and (4S,5S)-streptopyrrolidine (4) have been achieved in a concise and highly efficient manner via a highly stereoselective aldol type reaction with the trimethylsilyl enolate of ethyl acetate and Lewis acid mediated lactamization as the key reactions in ≈42

• (4S,5S)-streptopyrrolidine (4) in a concise and highly efficient manner via a highly stereoselective aldol type reaction and Lewis acid mediated lactamization as the key reactions. A retrosynthetic analysis for streptopyrrolidine is depicted in Scheme 1. The synthesis was initiated from D

Stereoselectivity of supported alkene metathesis catalysts: a goal and a tool to characterize active sites

• Christophe Copéret

Beilstein J. Org. Chem. 2011, 7, 13–21, doi:10.3762/bjoc.7.3

• high conversions; further underlining the need for highly stereoselective as well as stereospecific catalysts. Finally, it also shows that monitoring the stereoselectivity at low conversions (E/Z)0 can be very helpful in obtaining molecular information about the structure of the active sites and also

Highly substituted benzannulated cyclooctanol derivatives by samarium diiodide-induced cyclizations

• Jakub Saadi,
• Irene Brüdgam and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, 1229–1245, doi:10.3762/bjoc.6.141

• samariumorganyl intermediate, was always trans to the hydroxyl group, arising from the ketone moiety. This interesting observation indicates that the protonation is highly stereoselective and the protons are coming from the same face of the ring where the samariumoxy group is situated after the completed

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• extensively studied in the past. Highly stereoselective reactions of enantiopure nitrones allow rapid access to functionalized intermediates that have been elegantly used for the preparation of a wide range of natural products [9]. It is known that pre-complexation of carbohydrate-derived nitrones by Lewis

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• oxygen functions onto an unsaturated, non-functionalized carbon skeleton 271. Diversity in this approach arose from the relative timing of highly stereoselective reactions, such as the Sharpless AD reaction and the Kennedy oxidative cyclization (OC) with rhenium(VII) oxide. The convergent strategy, which

The enantiospecific synthesis of (+)-monomorine I using a 5-endo- trig cyclisation strategy

• Malcolm B. Berry,
• Donald Craig,
• Philip S. Jones and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2007, 3, No. 39, doi:10.1186/1860-5397-3-39

• agreement with published values. [25] Short reaction times were found to be crucial to the success of this reaction. In summary, we have developed a highly stereoselective 5-endo-trig cyclisation reaction that facilitates the preparation of 2,5-syn disubstituted pyrrolidines. We have used this

Single and double stereoselective fluorination of (E)-allylsilanes

• Marcin Sawicki,
• Angela Kwok,
• Matthew Tredwell and
• Véronique Gouverneur

Beilstein J. Org. Chem. 2007, 3, No. 34, doi:10.1186/1860-5397-3-34

• chirality when reacting allylsilanes B with electrophiles other than fluorine. [18][19][20][21] Chiral allylsilanes B are known to act as useful carbon nucleophile equivalents in highly stereoselective condensation reactions with a large range of electrophiles leading to the construction of C-C, C-O, C-N or

Flexible synthesis of poison- frog alkaloids of the 5,8-disubstituted indolizidine- class. II: Synthesis of (-)-209B, (-)-231C, (-)-233D, (-)-235B", (-)-221I, and an epimer of 193E and pharmacological effects at neuronal nicotinic acetylcholine receptors

• Soushi Kobayashi,
• Naoki Toyooka,
• Dejun Zhou,
• Hiroshi Tsuneki,
• Tsutomu Wada,
• Toshiyasu Sasaoka,
• Hideki Sakai,
• Hideo Nemoto,
• H. Martin Garraffo,
• Thomas F. Spande and
• John W. Daly

Beilstein J. Org. Chem. 2007, 3, No. 30, doi:10.1186/1860-5397-3-30

• the resulting aldehyde under Stork's conditions [11] provided the Z-iodoolefin 5 in a highly stereoselective manner. The Sonogashira coupling reaction [12] of 5 with TMS-acetylene followed by cleavage of the trimethylsilyl group with K2CO3 afforded (-)-231C. Although the rotation of the natural

Stereoselective α-fluoroamide and α-fluoro- γ-lactone synthesis by an asymmetric zwitterionic aza-Claisen rearrangement

• Kenny Tenza,
• Julian S. Northen,
• David O'Hagan and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2005, 1, No. 13, doi:10.1186/1860-5397-1-13

• highly stereoselective method for the preparation of α-fluoroamides. When the reaction was conducted without a fluorine in the substrate, using propionyl chloride in place of 2-fluoropropionyl chloride, then the diastereoselectivity decreased, generating 26 but in only 75% de. Thus the fluorine as well