Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• isomerisation to 1-tetralones with >99% stereoretention (Scheme 18) [53]. To obtain the starting material for the transformation (Scheme 18), the authors have described the addition of arylboronic acids to 3-substituted-2-cyclopentenones (Table 26) either by using Stoltz’s catalytic system L9/Pd(TFA)2 or by its

• ]. Addition reactions of arylboronic acids to substituted chromones catalysed by L9/Pd(TFA)2 [7]. Addition of various highly functionalized arylboronic acids to 3-methylcyclohexanone for the synthesis of terpenoids [10][11]. Addition reactions of arylboronic acids to 3-alkyl-2-cyclopentenones catalysed by L9

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• cyclized product was observed when using the trifluoromethyl ketone derivative 12d. Secondly, PKR with enynes 14 containing fluorinated propargyl alcohol groups yielded diastereoisomeric mixtures of pyrrolidine ring-fused cyclopentenones 15 in good yields (67–85%) but low diastereoselectivities. Finally

• synthesize trifluoromethylated nitrogen- and sulfur-based bicyclic compounds (Scheme 13) [53]. Using this methodology, the corresponding cyclopentenones 29 were isolated in generally good yields, except for sulfur-containing derivative 29c, due to the oxidation of the sulfide under the reaction conditions

• cyclopentenones 54 as single diastereoisomers (Scheme 28). In general, yields were moderate to good, and high diastereoselectivities were observed in almost all cases. The PKR tolerated both mono- and disubstituted olefins well, but when a trisubstituted olefin was assayed in the PKR, the initial enyne was

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• of 2-alkenylcyclopentanones 276 and cyclopentenones 277 [358]. Thus, the treatment of a solution of endoperoxides 275 in CH2Cl2 with triethylamine while increasing the temperature from 0 °C to room temperature affords hydroxyketone 276. The use of the stronger base DBU results in the formation of 2

• -vinyl-2-cyclopentenones 277 in high yield (Table 15). In the case of acyclic enamine 278, the initial dioxetane product from the photochemical oxidation of 279 rearranged to amide 280. The reactions using cyclic enamines 281 involve the Kornblum–DeLaMare rearrangement of dioxetanes 282 into 1,2

Novel carbocationic rearrangements of 1-styrylpropargyl alcohols

• Christine Basmadjian,
• Fan Zhang and
• Laurent Désaubry

Beilstein J. Org. Chem. 2015, 11, 1017–1022, doi:10.3762/bjoc.11.114

• : carbocationic rearrangement; cyclopentenones; furans; propargyl alcohols; Introduction In the course of our medicinal program on a new class of anticancer agents [1][2][3], we developed a novel synthesis of cyclopentenones substituted by three different aryl groups (Scheme 1) [4]. This approach combines a

• impossible to achieve [4][8][9]. The importance of cyclopentenones as intermediates to the synthesis of bioactive compounds prompted us to explore the synthetic potential of this novel rearrangement of 1-styrylpropargyl alcohols (Table 1). Toward this purpose, a number of other substrates were synthesized

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• from (1R,2S)-ephedrine, to α-substituted cyclopentenones. The required precursor for the synthesis of methyl jasmonate (11), 2-(2-pentynyl)-2-cyclopentene-1-one (148) was prepared by a known sequence [115] starting from 1,3-cyclohexanedione (145) (Scheme 18). Addition to 1-bromo-2-pentyne (146

Polar reactions of acyclic conjugated bisallenes

• Reiner Stamm and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 36–48, doi:10.3762/bjoc.9.5

• involving polar intermediates and/or transition states has been investigated on a broad scale for the first time. The reactions studied include lithiation, reaction of the thus formed organolithium salts with various electrophiles (among others, allyl bromide, DMF and acetone), oxidation to cyclopentenones

• transformations. Keywords: β-lactams; conjugated bisallenes; cyclopentenones; epoxidation; halogen addition; hydrohalogenation; ionic additions; metalation; Introduction Whereas the use of hexa-1,2,4,5-tetraene (1) and its derivatives in pericyclic reactions is well documented [2][3][4][5][6], relatively little

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• cyclopentenones [140]. Applying the mechanism discussed in this latter context to 24, it is reasonable to propose the formation of an allene-epoxide first [141], which can exist either in a transoid, 212, or cisoid conformation, 213 (Scheme 51). Whereas the former could open up to the “stretched” zwitterion 214

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

• [1,2]- and [1,3]-acyl migration of 2-vinylcyclobutanones, leading to cyclopentenones or cyclohexenones, respectively [15]. Danheiser and co-workers reported an oxyanion-accelerated [1,3]-rearrangement of in situ reduced 2-vinylcyclobutanones, by applying mixtures of LiBu3BH-MeLi and HMPT to give

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• range of silicon-based tethers and promoters have been investigated for use in the development of a silyl-tethered Pauson-Khand reaction. Background Since its discovery in 1973, the Pauson-Khand (P-K) reaction has become one of the principal methods for the construction of cyclopentenones.[1][2

• . Pagenkopf has shown that when the P-K cyclisation is carried out in 'wet' acetonitrile the cyclisation would proceed to give the cyclopentenones (Scheme 2).[8][9] The tethering strategy was not however successful in that although cyclisation gave the correct regiochemistry, the silicon tether is cleaved

• synthesised proving the reaction could be repeated and was not an anomaly. The results for the other silanes did not show the product of the reaction as cyclopentenones. The only identifiable product isolated from any of the other reactions was the silanol associated with hydrolysis of the silicon-oxygen bond

A convenient synthesis of γ-functionalized cyclopentenones

• Nour Lahmar,
• Taïcir Ben Ayed,
• Moncef Bellassoued and
• Hassen Amri

Beilstein J. Org. Chem. 2005, 1, No. 11, doi:10.1186/1860-5397-1-11

• /1860-5397-1-11 Abstract The synthesis of γ-functionalized cyclopentenones was carried out in a few steps, starting firstly with the preparation of nitroketonic intermediates 2, which were readily transformed into 1,4-diketones using the Nef conversion. The intramolecular cyclization of the γ-diketones

• 3 in a basic medium, led to the functionalized cyclopentenones 4. Keywords: Nef reaction; conjugated addition; nitroalkanes; 1,4-diketones; functionalized cyclopentenones; Introduction The cyclopentenones are considered as an important class of compounds because they are present in a large variety

• of natural products and in many important biologically active compounds [1][2][3][4][5][6] such as prostanoids, jasmonoids, rethrolones, methylenomycins and allylrethrones. In this paper, we wish to describe a new synthetic procedure for the preparation of γ-functionalized cyclopentenones 4 via a