Enantioselective total synthesis of putative dihydrorosefuran, a monoterpene with an unique 2,5-dihydrofuran structure

• Irene Torres-García,
• Josefa L. López-Martínez,
• Rocío López-Domene,
• Manuel Muñoz-Dorado,
• Ignacio Rodríguez-García and
• Miriam Álvarez-Corral

Beilstein J. Org. Chem. 2022, 18, 1264–1269, doi:10.3762/bjoc.18.132

• stereoselective kinetic resolution of allenol 3 via lipase AK-catalyzed acetylation [15]. In this way, unaltered, (−)-hydroxyallene 3 could be separated from (+)-acetyl derivative 9 through standard column chromatography (Scheme 3). Enantiomeric excesses of (−)-3 and (+)-9 were determined by chiral HPLC analyses

• solution of the allenol 3 (65 mg, 0.35 mmol) in acetone (2 mL) was added to a suspension of AgNO3 (120 mg, 0.70 mmol) in acetone (1.5 mL) in the absence of light, and the mixture was stirred at 40 °C overnight. Brine was added and the mixture was extracted with Et2O. The organic phase was dried over

• ) AgNO3, Me2CO, 75%. Racemic resolution of allenol 3 and synthesis of derivatives. a) Lipase AK, vinyl acetate, t-BuOMe, 30 °C, ((−)-(S)-3: 46%, 90% ee, (+)-(R)-9: 39%, 95% ee); b) N,N’-dicyclohexylcarbodiimide (DCC), dimethylaminopyridine (DMAP), (S) or (R)-(−)-α-methoxy-α-(trifluoromethyl)phenylacetic

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• concentrations of AuCl could be constructed. Finally, the various spheres were investigated regarding the catalytic effect of the local gold concentration on the hydroalkoxylation of γ-allenol 34 (Figure 8). Since all catalytic tests were carried out at the same overall gold concentration of 5 mM, it was very

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• Hg(OTf)2-catalyzed conditions at lower temperature (Scheme 56) [117]. Following a similar strategy, mercury chlorate (Hg(ClO4)2) had been employed successfully as a cheap alternative to precious metals salts in the cyclization of α-allenol derivatives 185 to differently substituted 2,5-dihydrofurans

• -allenol derivatives. b) Simplified mechanism. Hg(TFA)2-promoted cyclization of a γ-hydroxy alkene derivative. Synthesis Hg(II)-salt-mediated cyclization of allyl alcohol for the construction of ventiloquinone J. Hg(OAc)2-mediated cyclization as a key step for the synthesis of hongconin. Examples of Hg(II

Is the tungsten(IV) complex (NEt₄)₂[WO(mnt)₂] a functional analogue of acetylene hydratase?

• Matthias Schreyer and
• Lukas Hintermann

Beilstein J. Org. Chem. 2017, 13, 2332–2339, doi:10.3762/bjoc.13.230

• allenol 7 and alkenol 8 are impurities already present in distilled starting material. Thus, complex 1 does not show hydration activity against higher terminal alkynes. To further validate those negative results, we wished to demonstrate a positive activity of complex 1, namely the reported hydration of

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• these preparatively interesting four-membered ring compounds [64]. When an allene carries a hydroxy function, it is, of course, a special type of an enol (an allenol) and as such unstable. Yet, it may be generated as an intermediate to be employed in further transformations. Indeed, when α-diketones

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

• -allenol derivatives has been published [48][49]. The general reactivity of 2-azetidinone-tethered γ-allenols toward the regioselective hydroalkoxylation reaction was investigated with substrate 8a (R1 = Bn, R2 = TBS) using [PtCl2(CH2=CH2)]2, AgNO3, AuCl and AuCl3 as catalysts. [PtCl2(CH2=CH2)]2 and AgNO3

• five-membered oxacycle. A computational study (using density functional theory, DFT) of the above heterocyclization has been carried out [50]. The Au(III)-catalyzed cyclization of γ-allenol I (Figure 1) takes place regio- and stereoselectively through a 5-exo hydroalkoxylation because of a kinetic

• problem associated with the tuning of the regioselectivities of γ-allenol derivatives. It should be mentioned that one of the challenges for modern synthesis is to create distinct types of complex molecules from identical starting materials based solely on catalyst selection. As the stability of the

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

• by Markó et al., the yields are relatively lower. Keywords: allenic ketone; allenol; Cu(I) catalyst; oxidation; Introduction The oxidation of alcohols is one of many fundamental reactions in organic synthesis [1][2]. Usually, stoichiometric oxidants such as MnO2 [3], PCC [4], PDC [4], etc. were

• of 1-naphthyl-substituted 1h afforded 2h in 74% yield (Table 5, entry 8). Tri-substituted allenic alcohol 1j was also oxidized to the corresponding allenic ketone 2j in 91% yield (Table 5, entry 10). The reaction may be easily carried out on a 1 g scale: the oxidation of allenol 1k afforded the

• ); IR (neat) 2956, 2928, 2861, 1933, 1678, 1496, 1456, 1171, 1100 cm−1; Anal. calcd for C17H22O: C, 84.25; H, 9.15. found: C, 84.16; H, 9.50. 1 gram scale reaction of allenol 1k. The oxidation of 1l and 1m under 1 atm of oxygen. Screening of bases for the CuCl-catalyzed oxidation of 1aa. Screening of