Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• Radhakrishnan laboratory reported the Rh-catalyzed oxidative coupling of salicylaldehyde derivatives 151 with diazabicyclic alkenes 130a producing fused chromanone derivatives 152 (Scheme 27) [73]. It was determined alkyl- and methoxy-substituted salicylaldehydes resulted in a minor reduction of yield while

Construction of trisubstituted chromone skeletons carrying electron-withdrawing groups via PhIO-mediated dehydrogenation and its application to the synthesis of frutinone A

• Qiao Li,
• Chen Zhuang,
• Donghua Wang,
• Wei Zhang,
• Rongxuan Jia,
• Fengxia Sun,
• Yilin Zhang and
• Yunfei Du

Beilstein J. Org. Chem. 2019, 15, 2958–2965, doi:10.3762/bjoc.15.291

• biologically interesting chromone skeleton was realized by PhIO-mediated dehydrogenation of chromanones under mild conditions. Interestingly, this method also found application in the synthesis of the naturally occurring frutinone A. Keywords: chromanone; chromone; dehydrogenation; frutinone A; PhIO

• highly efficient method for the synthesis of this privileged class of heterocycles. For example, Kim and co-workers reported that chromones could be prepared via a Pd(II)-catalyzed [55][56][57] dehydrogenation of chromanone derivatives at 100 °C in DMSO (Scheme 1a) [58]. The synthesis of chromones could

• also be realized by DDQ-mediated dehydrogenation of chromanones under heating in dioxane (Scheme 1b) [3][59][60]. In 2005, Yang and co-workers reported that chromones could be formed by microwave irradiation of the corresponding chromanone reactants and N-bromosuccinimide (NBS) in the presence of a

Volatiles from the tropical ascomycete Daldinia clavata (Hypoxylaceae, Xylariales)

• Tao Wang,
• Kathrin I. Mohr,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 135–147, doi:10.3762/bjoc.14.9

• -4-chromanone (12) and 5-hydroxy-2-methyl-4-chromanone (13) were tentatively identified from their mass spectra. Compound 13, which exhibits antimicrobial activity, was previously isolated from various species of Daldinia [16][19][20][21][22] and several endophytic fungi, the latter of which have

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• either of the nitro group or the thioether group. The same year Wang and co-workers reported the enantioselective synthesis of spiro-chromanone-thiochroman compounds 175 catalyzed by a bifunctional indane-based thiourea 176 (Scheme 57) [78]. The cascade is initiated by the sulfa-Michael addition of 2

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• precatalyst 54 and DBU promoted enantioselective intramolecular cross-benzoin reaction of 55 to afford chromanone 56 in excellent yield and enantioselectivity (Scheme 34). The NHC-precatalyst is conveniently prepared from camphor in 5 steps [51]. NHC generated from the N-tert-butyl-substituted imidazolium

• condensation. Intramolecular cross-benzoin condensation between aldehyde and ketone moieties. Intramolecular crossed aldehyde-ketone benzoin reactions. Enantioselective intramolecular crossed aldehyde-ketone benzoin reaction. Chromanone synthesis via enantioselective intramolecular cross-benzoin reaction

Cyclization of ortho-hydroxycinnamates to coumarins under mild conditions: A nucleophilic organocatalysis approach

• Florian Boeck,
• Max Blazejak,
• Markus R. Anneser and
• Lukas Hintermann

Beilstein J. Org. Chem. 2012, 8, 1630–1636, doi:10.3762/bjoc.8.186

• containing 1, which is capable of undergoing a reversible conjugate addition to form an intermediate A devoid of an alkene functionality (Scheme 2). Rotation around the single bond to give B should be a fast process, and cyclization to a 2-chromanone C is then entropically favored. Eventually, the

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• very good example of this was published by Kalena et al. some years ago [87] who observed that 2-alkenyl-7-hydroxy-4-chromanone could undergo ortho photocycloaddition to afford the tetracyclic compounds shown in Scheme 28. The initial enol tautomerizes to the α,β-unsaturated ketone, which can be