Ring contraction and ring expansion reactions in terpenoid biosynthesis and their application to total synthesis

• Nicolas Kratena,
• Nicolas Heinzig and
• Peter Gärtner

Beilstein J. Org. Chem. 2026, 22, 289–343, doi:10.3762/bjoc.22.21

• and at the pendant olefin, to give a diol 107a, which can undergo a 1,2-alkyl shift delivering the universal precursor 108. From here, α-oxidation and dearomatisation gives taiwaniaquinone B (109), oxidative deformylation taiwaniaquinol B (110) and methylendioxy cyclisation taiwaniaquinol A (111). The

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• -catalysed Povarov reaction rather than with its own tautomer (Scheme 21a) [70]. Zhang and You developed a catalytic dearomatisation reaction of indoles 150 using similar chemistry, where the generated imine 151 now reacts intramolecularly with a pendant nucleophile and is further oxidised to a carbocation

Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents

• Yafei Guo and
• Syuzanna R. Harutyunyan

Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90

• an N-acyl-4-methoxypyridinium salt using a copper/phosphoramidite catalytic system (Scheme 3) [20][21]. The authors highlighted that the N-acylpyridinium salts were unstable species and that their instability affected the regioselectivity of the dearomatisation process upon the nucleophilic addition

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• a high temperature was needed (reflux at 153 °C for 4 hours), the desired products were isolated in good (53–91%) yields. The authors reported better results with the use of polyheterocyclic initial compounds. This can be explained by a dearomatisation step taking place in the transformation of

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• units, reductive PKS release and Knoevenagel condensation yield the benzaldehyde intermediate 88. Oxidative dearomatisation of 88 catalysed by the salicylate monooxygenase AteafoD gives 89, which is hydroxylated at C8 by the oxygenase AteafoF. The positioning of this newly formed hydroxy group forces

Fused bicyclic piperidines and dihydropyridines by dearomatising cyclisation of the enolates of nicotinyl-substituted esters and ketones

• Heloise Brice,
• Jonathan Clayden and
• Stuart D. Hamilton

Beilstein J. Org. Chem. 2010, 6, No. 22, doi:10.3762/bjoc.6.22

• : bicyclic; cyclisation; dearomatisation; enol ether; heterocycle; pyridine; quinoline; Introduction Oxidative [1][2][3] or reductive (nucleophilic) [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] dearomatising cyclisation reactions are effective strategies for rapidly building complexity

• scope of the dearomatisation can be extended to much less reactive nucleophiles with a more electron deficient aromatic acceptor [39][40][41]. Thus enolates of glycine esters 1 carrying isonicotinoyl or nicotinoyl N-substituents cyclise readily to yield bicyclic amino acid derivatives 2 (Scheme 1a for

Knorr- Rabe partial reduction of pyrroles: Application to the synthesis of indolizidine alkaloids

• Brendon S. Gourlay,
• John H. Ryan and
• Jason A. Smith

Beilstein J. Org. Chem. 2008, 4, No. 3, doi:10.1186/1860-5397-4-3

• reaction for the dearomatisation of aromatic substrates is an extremely practical and important tool for synthetic chemists and is used widely as a key step for the synthesis of natural products and molecules of biological interest [1]. However, the partial reduction of pyrrole is difficult as the high