Combination of gold catalysis and Selectfluor for the synthesis of fluorinated nitrogen heterocycles

• Antoine Simonneau,
• Pierre Garcia,
• Jean-Philippe Goddard,
• Virginie Mouriès-Mansuy,
• Max Malacria and
• Louis Fensterbank

Beilstein J. Org. Chem. 2011, 7, 1379–1386, doi:10.3762/bjoc.7.162

• the elucidation of the mechanism and Selectfluor was suggested to play the double role of promoting the oxidation of gold(I) to a gold(III) active species and also the electrophilic fluorination of the enamine intermediates. Keywords: cycloisomerization reactions; fluorinated pyrrolidines; gold

• summarized in Table 1. The reaction of 1a in the presence of commercially available Ph3PAuCl (5 mol %) and Selectfluor (1.1 equiv) in acetonitrile at rt afforded an inseparable mixture of pyrrolidines 3a in 75% yield and 4a in 17% yield (Table 1, entry 1). Difluoro derivative 4a was isolated as a single

• fluorinated pyrrolidines 3a, 4a and 2-pyrroline 5a are unknown and could be interesting building blocks for organic synthesis. Following the previous catalyst screening, we stuck with the use of PPh3AuCl as the catalyst and next investigated the effect of the concentration of 1a and the stoichiometry of

Synthesis of novel 5-alkyl/aryl/heteroaryl substituted diethyl 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates by aziridine ring expansion of 2-[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters

• Satish S. More,
• T. Krishna Mohan,
• Y. Sateesh Kumar,
• U. K. Syam Kumar and
• Navin B. Patel

Beilstein J. Org. Chem. 2011, 7, 831–838, doi:10.3762/bjoc.7.95

• substituted novel pyrroline derivatives have been synthesized by this methodology and the products can be used as key intermediates in the synthesis of substituted pyrrolines, pyrroles and pyrrolidines. Keywords: 5-alkyl/aryl/heteroaryl substituted 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates; aziridine; N

• materials in the preparation of substituted pyrroles, pyrrolines and pyrrolidines. The pyrrolines as well as pyrrolidines with substitution at the 2-position are important structural units in many natural products. A few of the natural products that contain 2-substituted pyrroline and 2-substituted

• at 100–110 °C for a period of 12 h, the mono ester 24 was isolated as the major product in 65% yield along with 10% of unreacted starting material and 10% of pyrroline derivative 23 (Scheme 3). The imine bond reduction in pyrrolines to pyrrolidines can be carried out by established procedures in

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• starting from allenyl cyclobutanols [23]. 1.2 Cyclopropylmethanols Cyclopropyl methanols can be used, alternatively, as pre-electrophiles in gold-catalyzed reactions. In 2008 Chan and co-workers developed an efficient synthetic route to pyrrolidines via a tandem amination/ring expansion of these substrates

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

• ; iminocyclitols; natural products; olefin metathesis; Ru-alkylidene catalysts; Review Introduction Synthetic and natural polyhydroxylated N-heterocyclic compounds (pyrrolidines, piperidines, piperazines, indolizines, etc., and higher homologues), commonly referred to as azasugars, iminosugars or iminocyclitols

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

• Streptomyces sp. found in deep sea sediments [12]. The system is present in many biologically active compounds [13][14][15][16][17][18][19][20][21] and it could act as a versatile intermediate for the synthesis of a wide range of γ-amino acids as well as pyrrolidines [22][23]. The interesting chemical

Prins fluorination cyclisations: Preparation of 4-fluoro-pyran and -piperidine heterocycles

• Guillaume G. Launay,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2010, 6, No. 41, doi:10.3762/bjoc.6.41

• methodology was extended to the aza-Prins reaction using N-tosyl-homoallylic amines to generate the corresponding 4-fluoropyrrolidines. In general, these reactions leading to both the 4-fluorotetrahydropyrans and 4-fluoro-pyrrolidines occur with good to high conversions, however the diastereoselectivities are

Diastereoselective functionalisation of benzo-annulated bicyclic sultams: Application for the synthesis of cis-2,4-diarylpyrrolidines

• Susan Kelleher,
• Pierre-Yves Quesne and
• Paul Evans

Beilstein J. Org. Chem. 2009, 5, No. 69, doi:10.3762/bjoc.5.69

• place to afford cis-2,4-diaryl-substituted pyrrolidines 35–37. Keywords: cyclic sulfonamides; diastereoselective alkene functionalisation; double reduction; Pd-mediated cross coupling; Introduction Substituted pyrrolidine ring systems represent a common structural motif in a range of biologically

• active compounds, including pharmaceutical agents and natural products. In relation to these general targets, we have recently developed a method that enables the construction of aryl-substituted pyrrolidines, featuring the double reduction of cyclic aromatic sulfonamides [1][2][3][4]. As illustrated in

• preparation of 2,4-diaryl-substituted pyrrolidines from more readily available, albeit racemic, substrates. Results and Discussion Bicyclic aromatic cyclic sulfonamides 5a and 5b were formed according to the 3-step sequence previously described [1][2][3][10]. Originally, inclusion of triphenylphosphine was

Radical cascades using enantioenriched 7-azabenzonorbornenes and their applications in synthesis

• David M. Hodgson and
• Leonard H. Winning

Beilstein J. Org. Chem. 2008, 4, No. 38, doi:10.3762/bjoc.4.38

• -azabenzonorbornadienes. Oxidation (using RuO4) and Birch reduction of the 2-aza-5,6-benzonorbornenes provide access to substituted pyrrolidines and tetrahydroindenes, respectively. Keywords: asymmetric synthesis; deoxygenation; radicals; rearrangements; tandem reactions; Introduction Carbon-centred radicals have been

• –oxidation with (−)-Ipc2BH to be determined by chemical correlation. Pyrrolidine 35 was independently prepared from (1R)-(−)-2-azabicyclo[2.2.1]hept-5-en-3-one (Vince’s lactam [36], 37) via reduction with LiAlH4, Boc-protection and oxidative cleavage [37] (Scheme 9). The pyrrolidines prepared from rearranged

• the intermediate radical undergoes rearrangement prior to electrophile trapping, thereby providing a new route to substituted 2-aza-5,6-benzonorbornenes. These adducts have been shown to lead on to pharmaceutically significant [40] (aminomethyl)indenes, and to substituted pyrrolidines and

C₂-symmetric bisamidines: Chiral Brønsted bases catalysing the Diels- Alder reaction of anthrones

• Deniz Akalay,
• Gerd Dürner,
• Jan W. Bats and
• Michael W. Göbel

Beilstein J. Org. Chem. 2008, 4, No. 28, doi:10.3762/bjoc.4.28

• exerted by chiral Brønsted bases. Moderate to excellent stereoselectivities of products 3 have been reported using pyrrolidines 4 [1][2], cyclic guanidine 5 [3], or cinchona alkaloids 6 [4] as catalysts. Recently, we could promote this type of cycloaddition by metal-free bisoxazolines 7 in up to 70% ee

Knorr- Rabe partial reduction of pyrroles: Application to the synthesis of indolizidine alkaloids

• Brendon S. Gourlay,
• John H. Ryan and
• Jason A. Smith

Beilstein J. Org. Chem. 2008, 4, No. 3, doi:10.1186/1860-5397-4-3

• confirmed by comparison of the spectral data with that reported by Huxtable who prepared 9 as an intermediate in the synthesis of lentiginosine [12]. For the partial reduction of electron rich pyrroles reported previously, over reduction to give pyrrolidines is a problematic side-reaction. For example

Desymmetrization of 7-azabicycloalkenes by tandem olefin metathesis for the preparation of natural product scaffolds

• Wolfgang Maison,
• Marina Büchert and
• Nina Deppermann

Beilstein J. Org. Chem. 2007, 3, No. 48, doi:10.1186/1860-5397-3-48

• -azabicycloalkenes by intra- and intermolecular tandem metathesis sequences with ruthenium based catalysts. Conclusion Desymmetrization of 7-azabicycloalkenes by olefin metathesis is an efficient process for the preparation of common natural product scaffolds such as pyrrolidines, indolizidines and isoindoles

• azabicycloalkane scaffolds was first described by Grubbs[23] for the synthesis of peptide mimetics and later extended by several other groups. [24][25][26][27][28][29][30][31] Key intermediates in these approaches are often alkenyl substituted pyrrolidines, which are N-acylated with an unsaturated carboxylic acid

• and submitted to a ring closing metathesis (RCM). As a part of a general synthetic concept using azabicycloalkenes as masked analogs of functionalized pyrrolidines or piperidines [32][33][34][35][36][37][38][39] we have previously applied the concept of intramolecular ring-opening/ring-closing

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

• University, Private Bag 11 222, Palmerston North, New Zealand 10.1186/1860-5397-3-39 Abstract We have developed a general strategy for the synthesis of 2,5-syn disubstituted pyrrolidines that is based on the multi-faceted reactivity of the sulfone moiety and a 5-endo-trig cyclisation. This methodology was

• , such as tetrahydrofurans and pyrrolidines, makes these motifs attractive targets for synthesis. Over the last decade we have developed a powerful general strategy for the preparation of such compounds based upon the multi-faceted reactivity of the sulfone group and the formally disfavoured 5-endo-trig

• mode of cyclisation. [1][2][3][4][5][6] The methodology allows the conversion of epoxides (X = O) or aziridines (X = N-PG) (2) into the desired trisubstituted tetrahydrofurans or pyrrolidines (5) via a series of sulfone-mediated transformations (Scheme 1). Ring-opening 2 with the sulfone-stabilised

An asymmetric synthesis of all stereoisomers of piclavines A1-4 using an iterative asymmetric dihydroxylation

• Yukako Saito,
• Naoki Okamoto and
• Hiroki Takahata

Beilstein J. Org. Chem. 2007, 3, No. 37, doi:10.1186/1860-5397-3-37

• monocyclic compounds (pyrrolidines) to bicyclic derivatives (indolizidines) provides rigid conformation and causes close proximity (a change from 1,5- to 1,3-relationship) between the two asymmetric centers. With indolizidine (5R, 8aR)-18 in hand, we examined partial-reduction of their triple bonds. First