Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• (173), which was then described in a 14-step strategy, starting from geraniol (169) [78]. Unlike compound 168, the installation of stereogenic centers at C14 and C15 was not sought at the 8-5 cyclization stage of the strategy, since formation of the tetrasubstituted alkene provided an adequate

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• ). An intermolecular [3 + 2] cycloaddition of tetrasubstituted alkene 150 and the dhdt-2-methanol reagent 151 under the effect of trifluoroacetic acid produced adduct 154 in 52% yield. The authors identified that the cyclic nature of the dhdt-2-methanol reagent 151 is essential for the cycloaddition to

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

• Clément Q. Fontenelle,
• Thibault Thierry,
• Romain Laporte,
• Emmanuel Pfund and
• Thierry Lequeux

Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160

• -opening reaction with bromide ions, even in the presence of bulky substituents. Keywords: acyclonucleotide; fluorine; monofluoroalkene; oxetane; selective ring-opening reaction; tetrasubstituted alkene; Introduction The introduction of fluorine atoms into organic compounds is known to modify their

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• tetrasubstituted alkene 11c was obtained as a 67:33 mixture of geometric isomers (Scheme 9) [33][34]. The rearrangement of secondary cyclopropenylcarbinyl acetates 10d–g could be achieved in the presence of Amberlyst® 15 and led exclusively to the (E)-alkylidene(acetoxycyclopropanes) 11d–g (E/Z > 99:1) in good

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• polymer-supported arsine 14 (0.008–0.04 equivalents) as the catalyst in related reactions (Figure 1) [12]. In this work, 14 was found to be the only arsine examined that was able to effectively catalyze Wittig-type reactions of ketone substrates to produce tri- and tetrasubstituted alkene products in very

Cyclization–endoperoxidation cascade reactions of dienes mediated by a pyrylium photoredox catalyst

• Nathan J. Gesmundo and
• David A. Nicewicz

Beilstein J. Org. Chem. 2014, 10, 1272–1281, doi:10.3762/bjoc.10.128

• in 68% yield, albeit with no diastereocontrol (2m, 1:1 dr; Table 3, entry 1). A diene bearing a tetrasubstituted alkene (2n) was reactive in this context, giving polycyclic endoperoxide 3n in 64% yield (6.5:1 dr). The use of 1,2-, 1,1-dialkyl as well as monoalkyl-substituted alkenes appeared to

Less reactive dipoles of diazodicarbonyl compounds in reaction with cycloaliphatic thioketones – First evidence for the 1,3-oxathiole–thiocarbonyl ylide interconversion

• Valerij A. Nikolaev,
• Alexey V. Ivanov,
• Ludmila L. Rodina and
• Grzegorz Mlostoń

Beilstein J. Org. Chem. 2013, 9, 2751–2761, doi:10.3762/bjoc.9.309

• most reactive diazodicarbonyl compound was diazoacetylacetone. In the case of dimethyl diazomalonate competitive 1,3-electrocyclization yielded the corresponding thiirane at elevated temperature, which after spontaneous desulfurization produced a tetrasubstituted alkene. To explain the observed

• the postulated structure of the 1,3-oxathiole ring [20]. The structure of the thiirane 8e was established based on the analogy of its main 1H and 13C NMR signals with a thiirane obtained previously from thiobenzophenone [6][21]. The structure of tetrasubstituted alkene 5e was confirmed based on a

• formation of a thiirane derivative, which after subsequent desulfurization is converted into the corresponding tetrasubstituted alkene. At an elevated temperature (80 °С) the process is shifted in this direction, evidently due to reversible interconversion of an intermediate thiocarbonyl ylide and the

Stereoselective synthesis of tetrasubstituted alkenes via a sequential carbocupration and a new sulfur–lithium exchange

• Andreas Unsinn,
• Cora Dunst and
• Paul Knochel

Beilstein J. Org. Chem. 2012, 8, 2202–2206, doi:10.3762/bjoc.8.248

• an intermediate biphenyllithium derivative of type 6, followed by an intramolecular ring-closing sulfur–lithium exchange [22] leading to the desired alkenyllithium 7 (Scheme 2). Subsequent quenching with a different electrophile E2 should afford the tetrasubstituted alkene of type 5; (Scheme 1

• was quenched with typical electrophiles with a high retention of the double-bond geometry. Thus, the treatment of 7a with EtI (2 equiv, −78 °C, 15 min) provides the tetrasubstituted alkene 5a in 75% yield and an E/Z ratio of 1:99. Direct carboxylation by the reaction with ethyl chloroformate (1.1

• tetrasubstituted alkene 4a. Synthesis of the alkenyllithium reagent 7a by an S–Li exchange. Quenching of the alkynyllithium 7a. (Product ratios and diastereoselectivities were determined by 1H- and 2D-NMR.) Synthesis and quenching of Z-styryllithium. Supporting Information Supporting Information File 218

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

• -opening. The alternative mechanism involves nucleophilic attack of 2-methylfuran on the gold carbene 51, followed by elimination (Scheme 23) [24]. The reaction was more difficult to carry out with cyclopropene carboxylates 52 and 53 possessing tetrasubstituted alkene structures. The former substrate