Gold-catalyzed oxycyclization of allenic carbamates: expeditious synthesis of 1,3-oxazin-2-ones

• Benito Alcaide,
• Pedro Almendros,
• M. Teresa Quirós and
• Israel Fernández

Beilstein J. Org. Chem. 2013, 9, 818–826, doi:10.3762/bjoc.9.93

• -1,3-oxazinan-2-one) 3g through a two-fold cyclization. This product particularly underlines the power of the present cyclization reaction, as none of the conventional methods would allow its synthesis with such great ease. Interestingly, as a first try, we were pleased to notice that the reaction of

• vacant d atomic orbital of the gold atom in INT1-B [79]. Both complexes can undergo the corresponding oxyauration cyclization reaction. Thus, INT1-A is converted into INT2-A in a slightly exergonic process (ΔGR,298 = −0.4 kcal/mol) through the saddle point TS1-A, which is associated with the 6-endo-dig

• cyclization. Similarly, INT1-B is transformed into INT2-B in a slightly endergonic process (ΔGR,298 = +0.9 kcal/mol) via TS1-B, associated with the 6-exo-dig cyclization reaction. From the data in Figure 1, it becomes obvious that the 6-endo-dig transformation is kinetically favored over the 6-exo-dig

Synthesis of meso-substituted dihydro-1,3-oxazinoporphyrins

• Satyasheel Sharma and
• Mahendra Nath

Beilstein J. Org. Chem. 2013, 9, 496–502, doi:10.3762/bjoc.9.53

• NaBH4 in a chloroform/methanol mixture at 25 °C produced meso-substituted aminoporphyrins 4 and 5, respectively. In the final step, these aminoporphyrins underwent a condensation cyclization reaction with aldehydes in THF under reflux to form new dihydro-1,3-benzoxazinoporphyrins 6–9 in good yields

• condensation–cyclization reaction of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (1) with α- or β-naphthol and formaldehyde in THF under reflux. After reaction with Zn(OAc)2·2H2O in CHCl3/MeOH mixture, the free-base naphthoxazinoporphyrins 14 and 16 underwent zinc insertion to afford zinc (II) dihydro-1,3

• -naphthoxazinoporphyrins 15 and 17 in 90–92% yields as depicted in Scheme 2. In addition, the dimeric naphthoxazinoporphyrins 18–20 were also prepared in moderate yields through one-pot Mannich-type condensation–cyclization reaction of 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (1) with α,α- or β,β- or α,β

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• cyclization reaction (Scheme 44). Under Nakamura’s iron-catalyzed carbometalation reaction conditions (shown in Scheme 17), the reaction of oxabicyclic alkenes provided ring-opened product 4m through a carbomagnesiation/elimination pathway (Scheme 45, reaction 4l to 4m) [82]. In contrast, the use of the 1,2

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

An efficient access to the synthesis of novel 12-phenylbenzo[6,7]oxepino[3,4-b]quinolin-13(6H)-one derivatives

• Wentao Gao,
• Guihai Lin,
• Yang Li,
• Xiyue Tao,
• Rui Liu and
• Lianjie Sun

Beilstein J. Org. Chem. 2012, 8, 1849–1857, doi:10.3762/bjoc.8.213

• terms of good yield, short reaction time and simple workup [37][41]. Upon use of PPA as the cyclization agent, we found that the cyclization reaction of 3a–h could be performed smoothly at 150 °C as shown in Scheme 3. After the reaction was completed (monitored by TLC), the reaction mixture was poured

• spectral data. The compounds 4a–h, newly synthesized in the present investigation, are listed in Table 2. As shown in Table 2, the cyclization reaction appears to be generally applicable, as most of the substrates 3 were consumed within 5–7 hours to give the corresponding cyclized products with reasonable

• the tert-butyl group during the cyclization reaction course. In addition, slow and gradual warming to the reaction temperature was also tried, but this had no effect on the outcome of the reaction. Thus, according to our previous experience [33], coupled with the fact that the tert-butyl substituent

Cyclization of ortho-hydroxycinnamates to coumarins under mild conditions: A nucleophilic organocatalysis approach

• Florian Boeck,
• Max Blazejak,
• Markus R. Anneser and
• Lukas Hintermann

Beilstein J. Org. Chem. 2012, 8, 1630–1636, doi:10.3762/bjoc.8.186

• considered a strategy to perform a fast catalytic conjugate addition of a heteronucleophile to the starting material in order to speed up the overall cyclization reaction. Initial experiments with neutral thiols as nucleophiles were not successful. On the other hand, addition of a nucleophilic

Synthesis of trifunctional cyclo-β-tripeptide templates

• Frank Stein,
• Tahir Mehmood,
• Tilman Plass,
• Javid H. Zaidi and
• Ulf Diederichsen

Beilstein J. Org. Chem. 2012, 8, 1576–1583, doi:10.3762/bjoc.8.180

• -phase chemistry [8][9]. Purification by chromatography is required after each coupling step, and the final cyclization reaction often results in poor yields. Herein, an alternative approach is described based on SPPS followed by on-resin cyclization. Recently, Waldmann et al. discovered an on-resin head

A macrolactonization approach to the total synthesis of the antimicrobial cyclic depsipeptide LI-F04a and diastereoisomeric analogues

• James R. Cochrane,
• Dong Hee Yoon,
• Christopher S. P. McErlean and
• Katrina A. Jolliffe

Beilstein J. Org. Chem. 2012, 8, 1344–1351, doi:10.3762/bjoc.8.154

• -F04a was synthesised by using a modified Yamaguchi macrolactonization approach. Alternative methods of macrolactonization (e.g., Corey–Nicolaou) resulted in significant epimerization of the C-terminal amino acid during the cyclization reaction. The D-stereochemistry of the alanine residue in the

The effect of the formyl group position upon asymmetric isomeric diarylethenes bearing a naphthalene moiety

• Renjie Wang,
• Shouzhi Pu,
• Gang Liu and
• Shiqiang Cui

Beilstein J. Org. Chem. 2012, 8, 1018–1026, doi:10.3762/bjoc.8.114

• an incomplete cyclization reaction and the existence of parallel conformations [55][56]. Among the three isomeric derivatives, the fluorescent modulation efficiency of diarylethene 2 was the largest and that of 1 was the smallest in PMMA films, suggesting that the diarylethene 2 is the best candidate

• process for the open-ring isomers 1o–3o occurs at higher potentials than in the corresponding closed-ring isomers 1c–3c. This was because the longer conjugation length of the closed-ring isomers generally leads to a less positive potential [62][65]. The cyclization reaction allows the π-conjugation to

Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size

• Patrick Claude,
• Christian Lehmann and
• Thomas Ziegler

Beilstein J. Org. Chem. 2011, 7, 1609–1619, doi:10.3762/bjoc.7.189

• ? Figure 11 illustrates what we intuitively anticipated at the beginning of the discussion, namely that the aromatic stacking interactions have a remarkable influence on the course of an intramolecular cyclization reaction: If the precyclized (seco) cyclic oxonium ion is modeled as an approximation for its

Synthesis of fluoranthenes by hydroarylation of alkynes catalyzed by gold(I) or gallium trichloride

• Sergio Pascual,
• Christophe Bour,
• Paula de Mendoza and
• Antonio M. Echavarren

Beilstein J. Org. Chem. 2011, 7, 1520–1525, doi:10.3762/bjoc.7.178

• cleanly in quantitative yield (Scheme 3). Derivatives 1a and 1b were readily prepared by the triple alkylation of the lithium anion of 4,9,14-trimethoxytruxene (Scheme 4) [41][62]. The cyclization reaction was carried out efficiently with gold(I) catalyst 6 (15 mol %) at room temperature in CH2Cl2 to give

Directed aromatic functionalization in natural-product synthesis: Fredericamycin A, nothapodytine B, and topopyrones B and D

• Charles Dylan Turner and
• Marco A. Ciufolini

Beilstein J. Org. Chem. 2011, 7, 1475–1485, doi:10.3762/bjoc.7.171

• -mediated cyclization reaction. This led to the formation of compound 35 in about 60% yield (based on 1H NMR; Scheme 6). A late intermediate in the Kelly synthesis of 1 [6][7] is structurally very similar to 35. Consequently, the preparation of 35 corresponds to a formal synthesis of fredericamycin A [31

Manganese dioxide mediated one-pot synthesis of methyl 9H-pyrido[3,4-b]indole-1-carboxylate: Concise synthesis of alangiobussinine

• Jessica Baiget,
• Sabin Llona-Minguez,
• Stuart Lang,
• Simon P. MacKay,
• Colin J. Suckling and
• Oliver B. Sutcliffe

Beilstein J. Org. Chem. 2011, 7, 1407–1411, doi:10.3762/bjoc.7.164

• glycolate (1) to manganese dioxide would result in the formation of aldehyde 2. This can then undergo a condensation process with tryptamine (3) allowing the generation of imine 4. This intermediate is set up appropriately to undergo a Pictet–Spengler cyclization reaction resulting in the formation of

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• -step reaction with, first, a Sonogashira coupling of o-haloanilines with terminal alkynes, followed by a cyclization reaction of the resulting 2-alkynyaniline derivatives [26][27]. A strategy for the preparation of indoles through a three-component reaction consisted of generating the terminal alkyne

• complex catalyzes the Sonogashira coupling and the cyclofunctionalization reaction. However, the presence of a strong electron-withdrawing substituent on the amino group is needed for the intramolecular cyclization reaction. Therefore, a protocol for a copper-free Sonogashira coupling was developed in

• , the Pd-mediated three-component reaction that gives access to the alkenylboronate 80 was followed by a palladium-mediated carbonylative cyclization reaction. Hydrogenation of the resulting unsaturated lactam 81 and removal of the N-benzyl group afforded rolipram (Scheme 34). Alper and coworkers

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

• electrophilic fluorine. Readily available 4-methyl-N-(pent-4-ynyl)benzenesulfonamide (1a) was used as a model substrate, and all the reactions were performed in anhydrous acetonitrile as the solvent. Various gold catalysts were screened. The results of the optimization of the cyclization reaction conditions are

• with 17% of 4a (Table 2, entry 2). Using lower amounts of Selectfluor raised the yield of 3a to 54% and 4a to 13% (Table 2, entry 3). In the presence of two equivalents of potassium carbonate the cyclization reaction did not occur (Table 2, entry 4). Lowering the temperature to 5 °C led to a dramatic

• flash chromatography being eluted first with petroleum ether and then with petroleum ether/ethyl acetate 9:1. Spectral data of cyclization precursors 1a. In agreement with the literature data [30][31]. 1b. In agreement with the literature data [31][32]. General procedure for the cyclization reaction

Gold(I)-catalyzed synthesis of γ-vinylbutyrolactones by intramolecular oxaallylic alkylation with alcohols

• Michel Chiarucci,
• Mirko Locritani,
• Gianpiero Cera and
• Marco Bandini

Beilstein J. Org. Chem. 2011, 7, 1198–1204, doi:10.3762/bjoc.7.139

• intermediates) [53][54][55] in the nucleophilic attack was excluded; non-enolizable compounds being suitable candidates for the cyclization reaction. Conclusions In conclusion, we have documented an unprecedented example of gold-catalyzed lactonization with primary allylic alcohols. Cationic NHCAu carbene gold

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

• cycloadduct by means of an intramolecular cyclization reaction, which generally proceeds with diastereoselectivities higher than 95:5 (Scheme 5). Interestingly, these cycloadditions can also be carried out in a highly enantioselective fashion using any of the bis(gold) complexes derived from (R)-C1-tunephos

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

• -activated alkene followed by a C–C bond cyclization reaction. The carbon, oxygen and nitrogen tethered 1,6-enynes react smoothly with methoxy substituted benzenes, indoles, pyrroles and furans as nucleophilic partners (Scheme 42). The cycloisomerization reactions of boronated enynes 233 was achieved with

• formed through a AuPPh3Cl catalyzed cyclization reaction [139]. Using gold complex [XPhosAu(NCCH3)SbF6] as the catalyst, Jurberg and Gagosz prepared the cinnoline derivatives 261 by the hydroarylation of N-propargyl-N-arylhydrazines 260 [140]. With the gold complex [Mes3PAu]NTf2, an alkynyl ether moiety

• cyclization of 1,3-enynyl ketones 297 [152]. The gold(III) catalyst exhibits dual roles for activating both the alkyne and carbonyl moieties (Scheme 51). More recently, Liu et al. developed a gold(III)-catalyzed tandem rearrangement/cyclization reaction of β-phenoxyimino ketone 299 (produced from O

A comparative study of the Au-catalyzed cyclization of hydroxy-substituted allylic alcohols and ethers

• Berenger Biannic,
• Thomas Ghebreghiorgis and
• Aaron Aponick

Beilstein J. Org. Chem. 2011, 7, 802–807, doi:10.3762/bjoc.7.91

• serve as leaving groups and obviate the need for a separate deprotection step. We reasoned that the best group to introduce would be one that was not susceptible to cleavage by standard deprotection conditions and therefore would only be removed after the desired cyclization reaction. Since alcohols are

Sequential Au(I)-catalyzed reaction of water with o-acetylenyl-substituted phenyldiazoacetates

• Lei Zhou,
• Yizhou Liu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2011, 7, 631–637, doi:10.3762/bjoc.7.74

• /cyclization reaction. Distilled water (0.5 mL) was added to a solution of complex 1 (0.5 mmol) and (IPr)AuCl (3 mol %, 9.3 mg) in DMF (1.5 mL) at room temperature under a N2 atmosphere. The reaction mixture was stirred for 24 h at 80 °C. After the mixture cooled to room temperature, it was diluted with ether

Gold-catalyzed heterocyclizations in alkynyl- and allenyl-β-lactams

• Benito Alcaide and
• Pedro Almendros

Beilstein J. Org. Chem. 2011, 7, 622–630, doi:10.3762/bjoc.7.73

• cyclization reaction has not been fully established, a possible reaction pathway has been proposed (Scheme 2) in which AuCl3 activates the allene group of 4-allenyl-2-azetidinones 1 to give 1-AuCl3. Subsequent cyclization affords 3, which then gives a transient vinyl–gold intermediate 4 [34][35][36][37

• oxycyclization/hydroxylation of 2-azetidinone-tethered alkynols for the synthesis of non-fused, spiro, and fused oxabicyclic β-lactams has been reported [65]. Attempts at a cyclization reaction of terminal alkynols using gold catalysts failed. However, under the appropriate reaction conditions was found that

Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes

• Yu-Hsuan Wang,
• Joshua F. Bailey,
• Jeffrey L. Petersen and
• Kung K. Wang

Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58

• -protropic rearrangement to form the corresponding benzannulated enyne–allene 10a. A Schmittel cyclization reaction [1][2][3][4] generates biradical 11a, which then undergoes an intramolecular radical–radical coupling to afford 12a. This is followed by a second prototropic rearrangement to restore the

• termini for the cascade cyclization reaction. Using a slightly different synthetic sequence from that shown in Scheme 3 but reminiscent of a sequence developed for the synthesis of 4,5-diheteroarylphenanthrenes [21], the benzannulated enediynes 19a and 19b were obtained (Scheme 4). It was gratifying to

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

• stereocenter was assigned based on NOESY-correlations and careful comparison of spectroscopic data with those of related compounds. The analogous cyclopentanone-derived starting material was also tested in the cyclization reaction; however, it afforded a complex mixture of products. Cyclization of acyclic

A novel and efficient method to prepare 2-aryltetrahydrofuran-2-ylphosphonic acids

• Vsevolod V. Komissarov,
• Anatoly M. Kritzyn and
• Jouko J. Vepsäläinen

Beilstein J. Org. Chem. 2010, 6, No. 63, doi:10.3762/bjoc.6.63

• mixture, reacts directly with the ketone 1 to produce intermediate 6 as shown in Scheme 2. The intermediate 6 rapidly forms ring 8 possibly via intermediate 7. However, the cyclization reaction in which hydroxyl group and chlorine atom are sterically near to each other are normally conducted under basic

• -aryl-1-butanones 1 with PCl3/AcOH lead to unexpected cyclic product 2 instead of the expected alkene 3. Preparation of cyclic furans 2a–e and ethyl esters 4a,c from chloroarylbutanones 1. Proposed reaction mechanism for the cyclization reaction. Acyclic products are obtained from pentanones 9a,b and

Synthesis of gem-difluoromethylenated analogues of boronolide

• Jing Lin,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2010, 6, No. 37, doi:10.3762/bjoc.6.37

• the key γ,γ-gem-difluoromethylenated α,β-unsaturated-δ-lactone scaffold could be constructed via an oxidation–cyclization reaction of intermediate A according to our published procedures [22]. cis-Selective reduction of homopropargyl alcohol B would provide the homoallylic alcohol A. The alcohol B