The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• good to excellent and the workup does not require chromatography of any kind. Many other (C3 + C3)-couplings have been reported in the chemical literature. For example, 2-butynyl halides 37 on treatment with Grignard reagents RMgBr provide hydrocarbons such as 3,4-dimethyl-1,2,4,5-hexatetraene (38

• %. Structurally comparable bisallene diols could be prepared, as shown by Krause and Poonoth [80][81], from bisoxiranes 100 by opening these with Grignard reagents in the presence of copper salts; this is again a double SN2'-process (Scheme 25). The resulting derivatives 101 are useful precursors for a double

C2-Alkylation of N-pyrimidylindole with vinylsilane via cobalt-catalyzed C–H bond activation

• Zhenhua Ding and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2012, 8, 1536–1542, doi:10.3762/bjoc.8.174

• sensitive to the amount of the Grignard reagent, as reduction of its loading from 100 to 60 mol % improved the yield of 3aa while suppressing the formation of byproduct 4 (Table 1, entry 10). Next, we performed screening of Grignard reagents using bathocuproine as the ligand (Table 2). Among Grignard

• reagents without β-hydrogen atoms, neopentyl- and phenylmagnesium bromides afforded 3aa in comparable yields (Table 2, entries 1 and 4), while trimethylsilylmethyl- and methylmagnesium chlorides gave much poorer results (Table 2, entries 2 and 3). Primary and secondary alkyl Grignard reagents also promoted

Synthesis of diverse indole libraries on polystyrene resin – Scope and limitations of an organometallic reaction on solid supports

• Kerstin Knepper,
• Sylvia Vanderheiden and
• Stefan Bräse

Beilstein J. Org. Chem. 2012, 8, 1191–1199, doi:10.3762/bjoc.8.132

• 10.3762/bjoc.8.132 Abstract The synthesis of diverse substituted indole structures on solid supports is described. The immobilization of nitrobenzoic acid onto Merrifield resin and the subsequent treatment with alkenyl Grignard reagents delivered indole carboxylates bound to solid supports. In contrast to

• with low yields) of the indole products. After optimization, we immobilized a number of nitrobenzoic acids onto solid supports. The resulting indoles after reaction with different Grignard reagents and subsequent cleavage are summarized in Table 1. In general, most of the nitroarenes were successfully

• converted to the indoles. As yields and purities were found to be higher when −40 °C and 3 equiv of Grignard reagents were used, we adopted these conditions for our library synthesis. Functional groups such as halides were tolerated. Two exceptions were the hydroxycarboxylic acids 1{f},1{j} and the

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• addition of an excess of organometallic reagents furnishing compounds of type C (Nu1 = Nu2) was described and discussed by Goti et al. (Scheme 1) [32]. In selected examples, the synthesis of differently substituted products (Nu1 ≠ Nu2) was possible by consecutive additions of the appropriate Grignard

• reagents [33]. Here we report on the application of a nitrone with an L-erythronolactone-derived auxiliary for the synthesis of 3,6-dihydro-2H-1,2-oxazine derivatives of type D. Their selected transformations, including hydroboration of the enol ether moiety, oxidative work-up, glycosyl cleavage, and

Efficient, highly diastereoselective MS 4 Å-promoted one-pot, three-component synthesis of 2,6-disubstituted-4-tosyloxytetrahydropyrans via Prins cyclization

• Naseem Ahmed and
• Naveen Kumar Konduru

Beilstein J. Org. Chem. 2012, 8, 177–185, doi:10.3762/bjoc.8.19

• ). Further, cleavage of the 4-tosyl group under mild conditions afforded 4-hydroxytetrahydropyran in excellent yields (95–96%). Results and Discussion The starting materials, aromatic homoallylic alcohols, were readily prepared by treatment of aromatic aldehydes with allylic Grignard reagents under a

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• started from dioxolane-diester 7 by reaction with 3-trifluoromethylphenyl or 3,5-bis(trifluormethylphenyl) Grignard reagents in the usual way to give TADDOLs T6 and T7 [92] in high yield (Scheme 5a). Interestingly, the reaction of o-trifluoromethylphenyl Grignard reagent with 7 gave hydroxyester 8 (Scheme

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• reaction of these Grignard reagents and transmetalation to zinc organometallics with ZnCl2 affords the expected products 101, 104 and 107 in 69–82% (Scheme 17 and Supporting Information File 1, Procedure 6) [9][22]. 2.3 Preparation of polyfunctional heterocyclic magnesium reagents by directed magnesation

Meta-metallation of N,N-dimethylaniline: Contrasting direct sodium-mediated zincation with indirect sodiation-dialkylzinc co-complexation

• David R. Armstrong,
• Liam Balloch,
• Eva Hevia,
• Alan R. Kennedy,
• Robert E. Mulvey,
• Charles T. O'Hara and
• Stuart D. Robertson

Beilstein J. Org. Chem. 2011, 7, 1234–1248, doi:10.3762/bjoc.7.144

• mixed-metal, mixed-anion reagents such as (TMPMgCl·LiCl) to perform regioselective functionalisation of aromatic and heteroaromatic compounds (TMP: 2,2,6,6-tetramethylpiperidide). Modified from their magnesiating “turbo-Grignard” reagents, Knochel’s three component system ((TMP)2Zn·2MgCl2·2LiCl) allows

A simple and convenient one-pot synthesis of substituted isoindolin-1-ones via lithiation, substitution and cyclization of N'-benzyl-N,N-dimethylureas

• Keith Smith,
• Gamal A. El-Hiti,
• Amany S. Hegazy and
• Benson Kariuki

Beilstein J. Org. Chem. 2011, 7, 1219–1227, doi:10.3762/bjoc.7.142

• ]. Also, some members that possess this moiety have shown interesting biological properties [9][10][11][12][13][14][15]. Several traditional methods are available for the synthesis of isoindolinones [16][17][18][19][20][21][22][23][24][25], based on the use of Grignard reagents [26], Diels–Alder reactions

Homocoupling of aryl halides in flow: Space integration of lithiation and FeCl₃ promoted homocoupling

• Aiichiro Nagaki,
• Yuki Uesugi,
• Yutaka Tomida and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2011, 7, 1064–1069, doi:10.3762/bjoc.7.122

• reoxidant, such as oxygen or other organic oxidants, are effective. Recently, iron salts have been also used because of their low costs and lack of toxicity [8][9][10][11][12][13][14][15][16][17][18]. For example, Hayashi et al. reported the iron-catalyzed oxidative homocoupling of Grignard reagents, using

• 1,2-dihalogenoethanes as an oxidant [19]. Cahiez et al. have also reported the FeCl3-catalyzed homocoupling reaction of Grignard reagents bearing functional groups, using atmospheric oxygen [20]. The use of aryllithium compounds instead of Grignard reagents is very interesting, because they are easily

The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

• Bryan Ringstrand,
• Martin Oltmanns,
• Jeffrey A. Batt,
• Aleksandra Jankowiak,
• Richard P. Denicola and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2011, 7, 386–393, doi:10.3762/bjoc.7.49

• single step from glutaconate diester and a Grignard reagent. However, this method is practically limited to simple 3-alkyl-1,5-pentanediols, such as 1a and 1b, since large excess of Grignard reagents is required. The second method, in which glutaric acids are obtained from aldehydes and malonate ester

Studies on Pd/NiFe₂O₄ catalyzed ligand-free Suzuki reaction in aqueous phase: synthesis of biaryls, terphenyls and polyaryls

• Sanjay R. Borhade and
• Suresh B. Waghmode

Beilstein J. Org. Chem. 2011, 7, 310–319, doi:10.3762/bjoc.7.41

• nonaflates [53], Grignard reagents with dihalobenzenes [54][55][56]: Other methods give poor yields. The Suzuki cross coupling protocol has been used for the synthesis of terphenyls and polyaryls using Pd(OAc)2 or Pd(PPh3)4 with or without ligands in homogeneous medium [57][58][59][60]. Although, these

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• (R = Me, Bu, sBu, Ph) was added to 30, a single isomer of the alkenylphosphonate 31 was obtained. Similarly, alkyl and aryl Grignard reagents as well as dialkylzinc compounds are transmetalated to their copper species and react regio- and stereoselectively with 30 (Scheme 15) [33]. S-substituted

Asymmetric synthesis of biaryl atropisomers by dynamic resolution on condensation of biaryl aldehydes with (−)-ephedrine or a proline- derived diamine

• Ann Bracegirdle,
• Jonathan Clayden and
• Lai Wah Lai

Beilstein J. Org. Chem. 2008, 4, No. 47, doi:10.3762/bjoc.4.47

• . A family of starting aldehydes 6a–f was made by the method of Meyers [36]. 2,3-Dimethoxybenzoic acid (1) was converted via its acyl chloride to oxazoline 3, from which the 2-methoxy group was displaced with a series of aryl Grignard reagents 4, yielding biaryloxazolines 5a–f (Scheme 1 and Table 1

Synthesis of chiral cyclohexanes and carbasugars by 6-exo-dig radical cyclisation reactions

• Rajeev K. Shrivastava,
• Elise Maudru,
• Gurdial Singh,
• Richard H. Wightman and
• Keith M. Morgan

Beilstein J. Org. Chem. 2008, 4, No. 43, doi:10.3762/bjoc.4.43

• corresponding aldehydes which on treatment with Grignard reagents afforded a mixture of alcohols. The corresponding iodides underwent similar 6-exo-dig cyclisation to give fully functionalised cyclohexanes. Keywords: carbasugars; cyclisation; cyclohexanes; 6-membered ring; stereoisomers; Introduction The use

Synthesis of densely functionalized enantiopure indolizidines by ring- closing metathesis (RCM) of hydroxylamines from carbohydrate- derived nitrones

• Marco Bonanni,
• Marco Marradi,
• Francesca Cardona,
• Stefano Cicchi and
• Andrea Goti

Beilstein J. Org. Chem. 2007, 3, No. 44, doi:10.1186/1860-5397-3-44

• methodology, several symmetrically α,α'-disubstituted hydroxylamines 1 were afforded. An alternative protocol for the synthesis of unsymmetrically α,α'-disubstituted hydroxylamines 3, resulting from the sequential addition of two different Grignard reagents, was also developed in a stepwise process, based on

• an addition-oxidation-addition sequence starting from N-glycosylhydroxylamine 4 (Scheme 2).[24] Addition of unsaturated Grignard reagents afforded synthetically useful hydroxylamine intermediates, which may serve as substrates for nitrogen ring forming reactions. We report in this article a

Synthesis of the Benzo- fused Indolizidine Alkaloid Mimics

• Daniel L. Comins and
• Kazuhiro Higuchi

Beilstein J. Org. Chem. 2007, 3, No. 42, doi:10.1186/1860-5397-3-42

• compounds. Results and Discussion The reaction of various kinds of heteroaryl Grignard reagents with the N-acylpyridinium salt prepared from 4-methoxypyridine (6) and 2-iodobenzoylchloride (7a) was studied (Table 1). The addition of 2-furyl [8], 2-thienyl [9] and 2-pyrrolyl [10][11] Grignard reagents gave N

• results, the reaction of 3-heteroaryl Grignard reagents was also examined (entries 6–9). The 3-furyl [16] and 3-thienyl [17] Grignard reagents were prepared from the corresponding 3-bromo compounds and gave 1f and 1g in moderate yields (entries 6,7). The compounds 1h and 1i were prepared in good yield

• biological activity. The various kinds of N-acyldihydropyridones 1 were conveniently prepared from heteroaryl Grignard reagents and N-acylpyridinium salts. Subsequently, dihydropyridones 1 were converted to 8 by use of an intramolecular Heck cyclization. The chloro- and nitro-substituted acyl chlorides 7

A divergent asymmetric approach to aza-spiropyran derivative and (1S,8aR)-1-hydroxyindolizidine

• Jian-Feng Zheng,
• Wen Chen,
• Su-Yu Huang,
• Jian-Liang Ye and
• Pei-Qiang Huang

Beilstein J. Org. Chem. 2007, 3, No. 41, doi:10.1186/1860-5397-3-41

• of enantiomeric malimide-based synthetic methodologies, [35][36][37][38] we now report concise and highly diastereoselective syntheses of an aza-spiropyran derivative 7 and (1S,8aR)-1-hydroxyindolizidine (ent-3). Results and discussion Previously, we have shown that the addition of Grignard reagents

Pd-catalysed [3 + 3] annelations in the stereoselective synthesis of indolizidines

• Olivier Y. Provoost,
• Andrew J. Hazelwood and
• Joseph P. A. Harrity

Beilstein J. Org. Chem. 2007, 3, No. 8, doi:10.1186/1860-5397-3-8

• phosphites have been reported using Grignard reagents [14]. In addition, 31P NMR studies showed that the addition of 1 equivalent of nBuLi to P(OPri)3 gave a mixture of P(OPri)3 and PBun3 after 15 minutes (See Supporting Information File 1 for details). Interestingly however, we have found PBun3 to be