Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• than sacrificial reductants/oxidants employed in conPET (e.g., tetraalkylammonium salts vs trialkylamines), it is worth emphasizing that electrolytes, generally, are chemically innocent to undesired reactions, whereas the byproducts of sacrificed amines may be involved in processes that lower the

A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones

• Yuki Yamamoto,
• Akihiro Tabuchi,
• Kazumi Hosono,
• Takanori Ochi,
• Kento Yamazaki,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 2906–2914, doi:10.3762/bjoc.17.198

• immediately from the reaction mixture containing n-Bu4N+OH−. Tetraalkylammonium salts are used as phase-transfer catalysts as they are soluble in both organic solvents and water. With these properties in mind, we next investigated the ring-closure of 2a using a two-phase CHCl3/H2O system (Table 2

Calixazulenes: azulene-based calixarene analogues – an overview and recent supramolecular complexation studies

• Paris E. Georghiou,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Hidetaka Nishimura,
• Jaehyun Lee,
• Atsushi Wakamiya and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2018, 14, 2488–2494, doi:10.3762/bjoc.14.225

• investigated. Keywords: azulene; calixarenes; calixazulenes; supramolecular chemistry; tetraalkylammonium salts; Introduction Among the great variety of synthetic macrocyclic molecular receptors which have been reported, those that are referred to by their generic name “calixarene” loom large [1][2][3]. The

• thermostated dual beam UV–vis spectrophotometer. Addition of microlitre aliquots of DCM solutions of the respective tetraalkylammonium salts (TRAX; where R = Me, Et; n-Bu and X = Cl−, Br−, I− or BF4−) resulted in quenching of the absorption spectra in the 300–700 nm range, with visible isosbestic points at

• state conditions, only 1:1 complexation modes between 5 and the respective tetraalkylammonium salts was considered. The binding constants were consistent with such an hypothesis. As a result, the DFT-generated complexes considered only such 1:1 “guest in cone” complexes, as shown in Figure 3a–f. Finally

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• provided crystallographic evidence that the alpha C–H bonds of tetraalkylammonium salts are highly polarized, and can form multiple hydrogen bonds with enolates in the solid state (Scheme 4) [40][41][42][43][44][45]. The existence of alpha C–H hydrogen bonds has also been invoked in the computational

• studies rationalizing the outcome of various asymmetric phase-transfer reactions [46][47][48][49]. However, despite these developments until recently [50][51] the use of tetraalkylammonium salts as hydrogen bond donor catalysts has not been explored. In 2011 the Park group investigated ammonium salts as

• atoms covalently bonded to a benzylic carbon (Scheme 8). In 2016 Maruoka and Shirakawa followed up the aforementioned studies by demonstrating that tetraalkylammonium salts L5, L6, L11 and L12 as well as TBAI could activate imines toward aza-Diels–Alder reaction with Danishefsky’s diene (Scheme 9) [51

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

• Roman Matthessen,
• Jan Fransaer,
• Koen Binnemans and
• Dirk E. De Vos

Beilstein J. Org. Chem. 2014, 10, 2484–2500, doi:10.3762/bjoc.10.260

• difficulty operating in organic solvents and under high pressure conditions, limiting operational conditions [44]. The anodic oxidation of more reduction stable tetraalkylammonium salts is another approach compatible with non-sacrificial anodes (Scheme 6c). Here, the released tetraalkylammonium cations

• function as counter ions for the cathodically formed carboxylate anions. If the corresponding oxidation products are not harmful for the cathodic reaction a simple undivided cell can be envisaged. However, this can also be considered as a sacrificial process, since the tetraalkylammonium salts are consumed

• the organic substrate, but only net conversion of more energetic oxalate and formate. On top of that, it is important to realize that both the MgO and the tetraalkylammonium salts can also be considered as sacrificial reducing agents. Their advantage over sacrificial anodes, however, is an easier

Cyclic phosphonium ionic liquids

• Sharon I. Lall-Ramnarine,
• Joshua A. Mukhlall,
• James F. Wishart,
• Robert R. Engel,
• Alicia R. Romeo,
• Masao Gohdo,
• Sharon Ramati,
• Marc Berman and
• Sophia N. Suarez

Beilstein J. Org. Chem. 2014, 10, 271–275, doi:10.3762/bjoc.10.22

• physical properties than most acyclic tetraalkylammonium salts. While cyclic phosphonium salts have been noted in patent applications [15], their characteristics have not been reported therein nor in journals, even though the comparisons noted above suggest those properties might be advantageous. To

Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives

• Carolin Regenbrecht and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2012, 8, 1721–1724, doi:10.3762/bjoc.8.196

• insoluble in the electrolyte. Precipitation occurs during the electrolysis when employing tetraalkylammonium salts in PC. This effectively prevents the desired products from over-oxidation. Since PC is environmentally benign and inexpensive, the procedure significantly improved the access to the