The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

Alkoxide-induced ring opening of bicyclic 2-vinylcyclobutanones: A convenient synthesis of 2-vinyl-substituted 3-cycloalkene-1-carboxylic acid esters

• Xiufang Ji,
• Zhiming Li,
• Quanrui Wang and
• Andreas Goeke

Beilstein J. Org. Chem. 2012, 8, 650–657, doi:10.3762/bjoc.8.72

• or acid derivatives makes this transformation a good supplementary method for the well-established Johnson–Claisen rearrangement. Keywords: alkoxide; cyclobutanones; esters; fused ring systems; ring opening; Introduction A great variety of methods are available for the synthesis of cyclobutane

• addition, the high electrophilicity of the carbonyl carbon atom, and the puckering of the cyclobutane caused by the substitution at C-2 and C-4, also offer both interesting preparative and mechanistic aspects [11]. The ease of ring opening of cyclobutanones is influenced by the strain of the four-membered

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

• bridging C–C bond and a formal [1,2]-alkynyl shift. Li et al. reported the first gold-catalyzed reaction of propargylcyclopropene systems 212 which affords benzene derivatives 213 in high yields [94] (Scheme 39). Only few efficient methods have emerged for the synthesis of cyclobutane derivatives, which

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

• Henning Hopf,
• Vitaly Raev and
• Peter G. Jones

Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

• ), photodimerization to the corresponding cyclobutane derivative occurs readily, and the photoproduct can be saponified to the corresponding pseudo-geminal diamine and truxinic acid (6) in excellent yield, thus allowing its stereospecific synthesis. We believe that the use of the [2.2]paracyclophane scaffold as a

• shown [22] by time-resolved photoelectron spectroscopy (TR-PES) that the pseudo-geminal divinyl derivative 7 can only react from its anti,anti-conformation (anti referring to the orientation of the vinyl substituent to the neighboring ethano bridge) to yield the cyclobutane derivative 8. The syn,anti

• any detectable photoproducts. The success in preparing cyclobutane derivative 4 (n = 1) from the corresponding cinnamophane diester 3 (n = 1, quantitative yield) led us to attempt to prepare the corresponding cyclobutane dialdehyde derivative 16 (Scheme 6). Unfortunately, although this was the only

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

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

• α to the carbonyl (construction of two fused cyclobutane ring systems) or delocalization of the radical to the para position can take place and the para product is formed. Non-classical photocycloadditions of alkenes with arenes Not only can the benzene moiety of arenes undergo cycloadditions upon

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• obtained for EYCM with styrenes. EYCM of terminal olefins with internal borylated alkynes. Synthesis of propenylidene cyclobutane via EYCM. Efficient EYCM with vinyl ethers. From cyclopentene to cyclohepta-1,3-dienes via cyclic olefin-alkyne cross-metathesis. Ring expansion via EYCM from bicyclic olefins

Synthesis of 2a,8b-Dihydrocyclobuta[a]naphthalene-3,4-diones

• Kerstin Schmidt and
• Paul Margaretha

Beilstein J. Org. Chem. 2010, 6, No. 76, doi:10.3762/bjoc.6.76

• ; quinone monoacetals; Introduction The behaviour of excited 1,2- and 1,4-quinones towards ground-state molecules differs greatly. Whereas the former typically react via H-abstraction by an excited carbonyl group [1], the latter smoothly undergo [2 + 2] cycloaddition to alkenes to afford cyclobutane-type

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

• product containing this basic skeleton is welwitindolinone A isonitrile (4); a compound that has recently captured the attention of the synthetic community [3][4]. Spiro[cyclobutane-1,3'-indolin]-2'-ones (3, n = 0) have previously been prepared but the synthetic approach is mostly limited to simple

Synthesis of a new class of aminocyclitol analogues with the conduramine D-2 configuration

• Latif Kelebekli,
• Yunus Kara and
• Murat Celik

Beilstein J. Org. Chem. 2010, 6, No. 15, doi:10.3762/bjoc.6.15

• acetic anhydride/CH3COONa [35] (Scheme 3). Careful examination of the reaction mixture did not reveal the formation of the other isomer. The stereochemical course of the hydroxylation may be syn or anti with respect to the oxazolidinone and cyclobutane rings. NMR spectroscopic studies did not allow the

Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• the molecule. This rules out symmetrical cycloadditions such as the 9,9′ : 10,10′ [4+4]reaction of anthracenes [11], whether combined or not with two cyclobutane-forming [2+2]additions. Dissymmetrical closures [11][12] such as 1,4 : 9′,10′ [4+4] or 1,4 : 2′,3′[4+2]cycloadditions (as well as rearranged

• carbons (54.9 to 66.0 ppm) and finally 4 to CH2 (31.6 to 36.5 ppm), attributable to the ethanocyclophane bridges. In previously studied cyclophanes, the cyclobutane rings exhibited 13C signals between 42 and 51 ppm [18][19]. No such signals are apparent in the present case; therefore it is proposed that

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

• the synthesis of spiro[2][5]octanes, an structural moiety of interest in the synthesis of natural products. Alcohols as 40 containing an allylsilane unit, which can be readily obtained by reaction of epoxides with the silylcuprate 2, are excellent synthons for cyclobutane ring-formation. Formation of

• . Intramolecular cyclization of TMS-epoxyallylsilanes. Spiro-cyclopropanation from oxoallylsilanes. Cyclobutane formation from hydroxy-functionalized allysilanes. Cyclobutene formation from vinyltin cuprates and epoxides. Silylcupration of 1,2-propadiene and reaction with α,β-unsaturated nitriles. Cycloheptane