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

• Phebox-based rhodium complex (C3) to catalyze the tandem conjugate addition of a terminal alkene followed by reacting the bicyclic dienol silyl ether intermediate with Michael acceptors in a one-pot procedure (Scheme 50) [92]. The bridged cyclic products 196a,b, formed by a double Michael addition

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• ) as a co-solvent. Nevertheless, capitalizing on these results, Cahiez further developed this iron-catalyzed cross coupling reaction with dienol phosphates as electrophiles, which are thermally more stable than dienyl halides [20]. It was found that when dienol phosphates were used as electrophiles

• , dialkyl phosphates used as leaving groups lead to overall transformations which display a poor atom economy. Moreover, diethyl chlorophosphate (DCP), used as a classic starting material in the dienol phosphates synthesis, is also registered under REACH regulation, and its use brings several toxicity

• issues for living organisms [25][26]. Additionally, the classic stereoselective synthesis of dienol phosphates requires cryogenic temperatures (−78 °C) as well as NMP-based methodologies [27]. Therefore, motivated by those considerations, we sought a suitable efficient and non-toxic additive which would

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• -dimethylallyl motif to 5 giving 17, followed by the anionic oxy-Cope rearrangement of the dienol into cyclohexenone 18. After desaturation, the resulting 2,5-cyclohexadienone 19 would provide a modular platform to construct the side chain of the target and analogues. Note that this updated route required the

Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

• Alex Frichert,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

• motif were prone to aromatization and had to be protected from contact with air and higher temperatures. Removal of solvents was performed below 21 °C and all compounds were stored under argon at −18 °C. Sonogashira coupling (PdCl2(PPh3)2) of dienol triflate 11 with alkyne 12 [11] provided C20 ester 13

• place. Thus, we reduced the ester function of dienol triflate 11 to the alcohol (DIBAL-H, DCM, −78 °C), followed by oxidation to aldehyde 15 (IBX, Scheme 2). Fortunately, the cyclohexadiene moiety survived the oxidation conditions, which was not the case when using PCC or MnO2. Subsequent Sonogashira

Synthesis and enzymatic ketonization of the 5-(halo)-2-hydroxymuconates and 5-(halo)-2-hydroxy-2,4-pentadienoates

• Tyler M. M. Stack,
• William H. Johnson Jr. and
• Christian P. Whitman

Beilstein J. Org. Chem. 2017, 13, 1022–1031, doi:10.3762/bjoc.13.101

• . The implications of these findings are discussed. The availability of these compounds will facilitate future studies of the haloaromatic catabolic pathways. Keywords: dienol; enzyme kinetics; fluoride; halogen; Introduction Aromatic hydrocarbons and their halogenated derivatives are well known

• faster conversion of the dienols to the β,γ-unsaturated ketones [14]. Hence, we only examined the ketonization of the dienols to the β,γ-unsaturated ketones (following the loss of the λmax associated with the dienol). The steady-state kinetic parameters for the 4-OT-catalyzed ketonization of 3b–d (to 10b

• enable a rough comparison of the relative activities of the Pp and Lc 4-OTs, the absorbance at 232 nm was monitored for a longer time period with identical amounts of dienol (150 μM, Figure S1 in Supporting Information File 1). In the presence of 150 μM of 5a, the Pp 4-OT (2 μM) generates 120 μM of 9a in

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• enantioselectivity encouraged the Inomata group to further investigate the reaction [152]. Their investigation of enantioselective hetero-Diels–Alder reactions resulted in an enantioselectivity of up to 92% ee, when nitrosobenzene and a dienol were reacted in the presence of tartaric acid ester as a chiral auxiliary

Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• the 1,4-dienol syntheses are summarised in Table 1. The cobalt-catalysed hydrovinylation tolerates halide, ether, ester, trifluoromethyl and heterocyclic substituents and gave the desired products in acceptable to good yields over a two-step reaction sequence of hydrovinylation and deprotection

• -dienols were transformed into cyclic phenylselenoethers by intramolecular cyclisation using selenium cations generated by indirect electrolysis. The reaction was carried out by electrolysing a mixture of the 1,4-dienol, diphenyl diselenide and tetraethylammonium bromide in CH3CN at room temperature in an

• and pyran products 3m and 4m, the latter product is formed via a 6-endo-tet-type cyclisation, in an excellent combined yield of 93%. When the mixture of the 1,4-dienols (2n and 2o) was applied, the major regioisomer 2n gave the pyran exclusively in good yields, while the minor 1,4-dienol 2o resulted

Structure elucidation of female-specific volatiles released by the parasitoid wasp Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

• Armin Tröger,
• Teris A. van Beek,
• Martinus E. Huigens,
• Isabel M. M. S. Silva,
• Maarten A. Posthumus and
• Wittko Francke

Beilstein J. Org. Chem. 2014, 10, 767–773, doi:10.3762/bjoc.10.72

• , followed by oxidation, yielded the aldehyde 10, which was chain elongated by Wittig reaction with [(2E)-1-methylbut-2-en-1-yl]triphenylphosphonium bromide [17] to afford the protected dienol 11 as a mixture of 4 racemates. This was due to partial epimerization at position 2 of the aldehyde 10 and the less

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• stable five-ring sulfonium ylide from the methyl ester analogue of diazoester 11b has previously been reported [15]. We confirm these results with 11b; however, in addition to sulfonium ylide 21 we also isolated the dienol 22 as a minor byproduct. The latter compound likely results from a thermally

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• is regenerated. When using a dienol silyl ether such as 21 (Scheme 12) as the diene component, the formation of the (4 + 2) products can be justified in terms of an alternative mechanism consisting of a 5-exo nucleophilic attack of the silyl enol ether moiety on the electrophilically activated alkyne

• ]. Gold-catalyzed intramolecular (4 + 2) cycloadditions of unactivated alkynes and dienes [55]. Gold-catalyzed preparation of bicyclo[4.3.0]nonane derivatives from dienol silyl ethers [59]. Gold(I)-catalyzed intramolecular (4 + 2) cycloadditions of arylalkynes or 1,3-enynes with alkenes [60]. Gold(I

Application of the diastereoselective photodeconjugation of α,β-unsaturated esters to the synthesis of gymnastatin H

• Ludovic Raffier and
• Olivier Piva

Beilstein J. Org. Chem. 2011, 7, 151–155, doi:10.3762/bjoc.7.21

• ester to its β,γ-unsaturated isomer through the protonation of a in situ generated dienol as key step. Thanks to diacetone D-glucose used as a chiral alkoxy group, the protonation occurred well onto one of the two diastereotopic faces with very high yields and selectivities. Moreover, by this way the

• configuration of the C-6 centre of the target molecule was controlled. Keywords: amide; diastereoselective protonation; dienol; isomerisation; Wittig reaction; Introduction The photodeconjugation of α,β-unsaturated esters 1 – which bear at least one hydrogen atom on γ-position – allows a straightforward

• from a [1,5]-sigmatropic rearrangement). It was shown that the efficiency of the isomerisation process is highly dependent on the nature of the solvent and on the presence of various additives (e.g., amines) which could catalyse the reketonisation of the transient dienol [4] (Scheme 1). Despite the