When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• alkene or an allene, the corresponding substrates 93 and 94 underwent a gold-catalyzed rearrangement to afford indenes 95 (80%) and 96 (78%), respectively. Interestingly, only the cyclopropene reacted by ring-opening followed by Friedel–Crafts cyclization: The alkene and the allene units were unaffected

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

• which rely on the activation of the allene and alkyne component. The mechanism as well as the regio- and stereoselectivity of the cyclizations are also discussed. Keywords: alkynes; allenes; gold; heterocyclizations; β-lactams; Introduction The chemistry of alkynes and allenes has been extensively

• catalyzed by gold complexes because of their powerful soft Lewis acidic nature [10][11][12][13][14][15][16]. In particular, gold-catalyzed intramolecular addition of oxygen and nitrogen nucleophiles across an allene or a carbon–carbon triple bond is intriguing from the point of view of regioselectivity

• four-membered ring, using the chirality and functionalization of the β-lactam ring as a stereo-controlling element [29][30]. This overview focuses on gold-catalyzed heterocyclization reactions of allenic and alkynic β-lactams which rely on the activation of the allene and alkyne component. The

Complete transfer of chirality in an intramolecular, thermal [2 + 2] cycloaddition of allene-ynes to form non-racemic spirooxindoles

• Kay M. Brummond and
• Joshua M. Osbourn

Beilstein J. Org. Chem. 2011, 7, 601–605, doi:10.3762/bjoc.7.70

• Kay M. Brummond Joshua M. Osbourn University of Pittsburgh, Department of Chemistry, Chevron Science Center, 219 Parkman Avenue, Pittsburgh, PA 15260, USA 10.3762/bjoc.7.70 Abstract A thermal [2 + 2] cycloaddition reaction of allene-ynes has been used to transform chiral non-racemic allenyl

• oxindoles into chiral non-racemic spirooxindoles containing an alkylidene cyclobutene moiety. The enantiomeric excesses were determined by chiral lanthanide shift NMR analysis and the transfer of chiral information from the allene to the spirooxindole was found to be greater than 95%. Keywords: alkylidene

• cyclobutene; allene; allenyloxindole; chiral lanthanide shift reagent; chiral transfer; Introduction The [2 + 2] cycloaddition reaction of allenes and alkynes provides rapid entry into synthetically challenging alkylidene cyclobutene ring systems. We, along with others, have demonstrated the intramolecular

Gold-catalyzed regioselective oxidation of terminal allenes: formation of α-methanesulfonyloxy methyl ketones

• Yingdong Luo,
• Guozhu Zhang,
• Erik S. Hwang,
• Thomas A. Wilcoxon and
• Liming Zhang

Beilstein J. Org. Chem. 2011, 7, 596–600, doi:10.3762/bjoc.7.69

• from terminal allenes in fair to good yields. The chemistry relies on a gold-catalyzed intermolecular oxidation of the 1,2-diene unit using 3,5-dichloropyridine N-oxide as the oxidant. The reaction tolerates a range of functional groups and shows excellent regioselectivity. Keywords: allene; catalysis

• allenes could also be oxidized by these N-oxides in the presence of gold catalysts. As shown in Scheme 1B, intermediate C, likely formed via an initial nucleophilic attack of a gold-activated allene, cannot undergo elimination in the same way as intermediate A, hence gold carbene intermediate B would not

• be formed. While C may revert back to the allene substrate, we suspect that a SN2'-type reaction by an external nucleophile could facilitate the fragmentation of the O–Y bond, ultimately leading to useful products via intermediate D. Herein we report our preliminary studies, which led to a facile

Synthesis of cross-conjugated trienes by rhodium-catalyzed dimerization of monosubstituted allenes

• Tomoya Miura,
• Tsuneaki Biyajima,
• Takeharu Toyoshima and
• Masahiro Murakami

Beilstein J. Org. Chem. 2011, 7, 578–581, doi:10.3762/bjoc.7.67

• stereoselective manner to give cross-conjugated trienes, which are different from those obtained by a palladium catalyst. Keywords: allene; cross-conjugated triene; dimerization; rhodium; stereoselective; Introduction Cross-conjugated trienes, known as [3]dendralenes [1], are attractive synthetic precursors

• of cross-conjugated trienes by the allene dimerization reactiona. Supporting Information Supporting Information File 110: Experimental details and spectroscopic data for new compounds. Acknowledgements This work was supported in part by MEXT (Grant-in-Aid for Challenging Exploratory Research, No

Synthesis of chiral mono(N-heterocyclic carbene) palladium and gold complexes with a 1,1'-biphenyl scaffold and their applications in catalysis

• Lian-jun Liu,
• Feijun Wang,
• Wenfeng Wang,
• Mei-xin Zhao and
• Min Shi

Beilstein J. Org. Chem. 2011, 7, 555–564, doi:10.3762/bjoc.7.64

• NHC–Au(I) complex (S)-6a was consequently investigated as the catalyst in the asymmetric intramolecular hydroamination of allenes. This reaction has been achieved with high enantioselectivity by a chiral phosphine–Au(I) complex [87][88][89][90][91][92][93]. Treatment of allene 11 with (S)-6a and

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• higher aromatics are more likely to undergo para cycloadditions [91], and that it is the main mode when allenes are involved [92]. A high yielding example of a para photocycloaddition with an allene has been published by Haddaway et al. (Scheme 30) [93]. If the irradiation is carried out in the presence

• photocycloaddition followed by rearrangements. Stable [2 + 2] photocycloadducts. Ortho photocycloadditions with alkynes. Intramolecular ortho photocycloaddition and rearrangement thereof. Intramolecular ortho photocycloaddition to access propellanes. Para photocycloaddition with allene. Photocycloadditions of

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

• Benzannulated enyne–allenes bearing an aryl substituent at the alkynyl terminus are excellent precursors of 5-aryl-11H-benzo[b]fluorenes [1][2][3][4][5]. Several synthetic pathways to the benzannulated enyne–allene systems have been reported, including generation in situ from the corresponding benzannulated

• enediynes. Specifically, treatment of the benzannulated enediyne 1a with potassium tert-butoxide in refluxing toluene for six hours promoted a 1,3-prototropic rearrangement to produce, in situ, the benzannulated enyne–allene 2a, which in turn underwent a sequence of Schmittel cascade cyclization reactions

• -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

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

• -closure; 1,3-hydrogen shift; isomerization; Introduction While allene isomerization to afford conjugated dienes is a well-known and thermodynamically favourable process, it is not trivial kinetically. A concerted allene isomerization leading to a diene involves a 1,3-hydrogen shift, which constitutes a

Rh(I)-catalyzed intramolecular [2 + 2 + 1] cycloaddition of allenenes: Construction of bicyclo[4.3.0]nonenones with an angular methyl group and tricyclo[6.4.0.0^1,5]dodecenone

• Fuyuhiko Inagaki,
• Naoya Itoh,
• Yujiro Hayashi,
• Yumi Matsui and
• Chisato Mukai

Beilstein J. Org. Chem. 2011, 7, 404–409, doi:10.3762/bjoc.7.52

• tricyclo[6.4.0.01,5]dodecenone framework in a satisfactory yield. Keywords: allene; bicyclo[4.3.0] derivatives; carbonylative [2 + 2 + 1] cycloaddition; quaternary center construction; rhodium; Introduction The Co2(CO)8-mediated Pauson–Khand reaction (PKR) [1][2] is well recognized as a formal [2 + 2 + 1

• allene group in the presence of several Rh(I) catalysts ([RhCl(CO)2]2, [RhCO(dppp)2]Cl or [RhCl(CO)dppp]2). We have now examined the similar ring-closing reaction using an alternative allenene 7a with a methyl group on the allenyl group for further evaluation of these reactions. According to the

• proximal double bond of the allene might be mandatory. Removal of the allylic sulfone group in 2a was achieved by tributyltin hydride in the presence of AIBN to give 9g in 91% yield [35][36][37][38][39][40][41]. Thus, the phenylsulfonyl group of 2a can be regarded as a hydrogen surrogate and this procedure

CuCl-catalyzed aerobic oxidation of 2,3-allenols to 1,2-allenic ketones with 1:1 combination of phenanthroline and bipyridine as ligands

• Shuxu Gao,
• Yu Liu and
• Shengming Ma

Beilstein J. Org. Chem. 2011, 7, 396–403, doi:10.3762/bjoc.7.51

• coordinating ability of the allene moiety. Further study in this area is being pursued in this laboratory. Experimental General experimental methods for starting materials The starting allenols 1a–e, 1i, 1k, 1l, 1m were prepared via the reaction of propargyl bromides and corresponding aldehydes in the presence

Allene chemistry

• Kay M. Brummond

Beilstein J. Org. Chem. 2011, 7, 394–395, doi:10.3762/bjoc.7.50

• continued in my first faculty position at West Virginia University, where my colleagues Professors Bob Moore (of the Doering-Moore-Skattebøl reaction) and Kung Wang (contributor to this issue) contributed greatly to my appreciation and understanding of the allene functional group. Focusing on a particular

• , creates a limitation to our knowledge of our field. This Thematic Series entitled “Allene chemistry” in the Beilstein Journal of Organic Chemistry represents contributions from leading chemists exploring a wide range of reactions involving allenes as reactants or products. The articles within detail

• discoveries surrounding the allene group and provide knowledge that chemists need in order to make informed decisions about whether or not to include an allene in a synthetic plan. I would like to thank all the authors for their contributions to this issue. Kay Brummond Pittsburgh, April 2011

C–C (alkynylation) vs C–O (ether) bond formation under Pd/C–Cu catalysis: synthesis and pharmacological evaluation of 4-alkynylthieno[2,3-d]pyrimidines

• Dhilli Rao Gorja,
• K. Shiva Kumar,
• K. Mukkanti and
• Manojit Pal

Beilstein J. Org. Chem. 2011, 7, 338–345, doi:10.3762/bjoc.7.44

• potential inhibition of TS [15]. The CMe2OH group next to the alkynyl moiety may facilitate the binding of the TS enzyme through its sulfhydryl (–SH) moiety with compounds 3f and 3g thereby generating the corresponding drug–enzyme allene intermediates (Figure 2). Nevertheless, the present study indicated

A thermally-induced, tandem [3,3]-sigmatropic rearrangement/[2 + 2] cycloaddition approach to carbocyclic spirooxindoles

• Kay M. Brummond and
• Joshua M. Osbourn

Beilstein J. Org. Chem. 2010, 6, No. 33, doi:10.3762/bjoc.6.33

• -2-one and an alkyne. The cycloaddition reaction occurs selectively with the distal double bond of the allene, is tolerant of a phenyl and trimethylsilyl group on the terminus of the alkyne, and can be used to access bicyclo[4.2.0]octadienes and bicyclo[5.2.0]nonadienes. The allene precursors are not

• observed, but are likely intermediates of an infrequently encountered thermal [3,3]-sigmatropic rearrangement of a propargylic acetate. Keywords: allene; propargylic acetate; spirooxindole; thermal [2 + 2] cycloaddition; thermal [3,3]-sigmatropic rearrangement; vinylidene indolin-2-one; Introduction

• discovery of new biological probes and pharmaceuticals [8]. We recently disclosed a thermal [2 + 2] cycloaddition reaction of allene-ynes to provide a variety of alkylidene cyclobutenes in good yields [9][10][11][12][13][14][15][16][17][18]. Notable features of this reaction were the stability of the

Synthesis of novel photochromic pyrans via palladium- mediated reactions

• Christoph Böttcher,
• Gehad Zeyat,
• Saleh A. Ahmed,
• Elisabeth Irran,
• Thorben Cordes,
• Cord Elsner,
• Wolfgang Zinth and
• Karola Rueck-Braun

Beilstein J. Org. Chem. 2009, 5, No. 25, doi:10.3762/bjoc.5.25

• ). Typically the thermal reversion of the open forms is very fast [17][18][19][20]. Quite recently, the formation of allene intermediates at low temperatures was also reported in the literature. They originate from open merocyanine isomers and are formed via a 1,5-hydrogen shift reaction [21][22]. However

• , these allene intermediates can be avoided by the replacement of hydrogen in the immediate vicinity of the two aryl residues (3-position of 2H-1-benzopyrans and 2-position of 3H-naphtho[2,1-b]pyrans). Thereby, the photochromism of benzo- and naphthopyrans is expected to be simplified for biological

Allylsilanes in the synthesis of three to seven membered rings: the silylcuprate strategy

• Asunción Barbero,
• Francisco J. Pulido and
• M. Carmen Sañudo

Beilstein J. Org. Chem. 2007, 3, No. 16, doi:10.1186/1860-5397-3-16

• key step is the syn addition of the tin cuprate to the acetylene, which controls the cis stereochemistry required for cyclization. [23] Seven Membered Carbocycles The use of nitriles and imines as electrophiles in the silylcupration of allene provides new alternatives for carbocyclization. Recently

• , we showed that α,β-unsaturated nitriles undergo a double addition process when treated with the cuprate species resulting from addition of 1 to allene, giving ketones 44 containing both an allylsilane group and a vinylsilane moiety (Scheme 10). [24] Equilibration between species 2 and 45 as the

Trapping evidence for the thermal cyclization of di-(o-acetylphenyl)acetylene to 3,3'-dimethyl- 1,1'-biisobenzofuran

• Charles P. Casey,
• Neil A. Strotman and
• Ilia A. Guzei

Beilstein J. Org. Chem. 2005, 1, No. 18, doi:10.1186/1860-5397-1-18

• oxygen on the near carbon of the alkyne produces intermediate B (Scheme 7). This attack might be catalyzed by protonation of a carbonyl by adventitious acid. The enolate (or enol) oxygen of B would then attack the central carbon of the allene, closing the second ring and forming biisobenzofuran A. In a