Germacrene B – a central intermediate in sesquiterpene biosynthesis

• Houchao Xu and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18

• reported from olibanum oil, but only identified from its mass spectrum and GC retention time [90]. This structural assignment in the absence of a reference standard or at least literature data for 20 is likely erroneous. Compound (−)-20 was later obtained by thermal degradation of (+)-maalian-5-ol (33

Heterogeneous metallaphotoredox catalysis in a continuous-flow packed-bed reactor

• Wei-Hsin Hsu,
• Susanne Reischauer,
• Peter H. Seeberger,
• Bartholomäus Pieber and
• Dario Cambié

Beilstein J. Org. Chem. 2022, 18, 1123–1130, doi:10.3762/bjoc.18.115

• colour of the polymer in the packed bed turned rapidly black (see Supporting Information File 1, Figure S4), and lower yields were observed (Table 1, entries 6 and 7). The catalyst deactivation could be due to the formation of nickel-black [28], or via (photo-)thermal degradation of the polymer. Packed

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• intramolecular H-bond character. The second protonation rather takes place on the N3 nitrogen atom, causing planar character disruption and preventing H-bonding (Figure 2) [1]. Biguanide derivatives often display low melting points (mp = 136 °C for simple biguanide). However, above 130 °C, a concomitant thermal

• degradation occurs leading to melamine derivatives via loss of ammonia. Hydrochloride and sulfate salts were shown to be more stable. The spectroscopic properties of biguanide are well documented [2]: neutral biguanide presents a maximum of absorption at 234 nm in UV spectrometry corresponding to the π–π

Effective microwave-assisted approach to 1,2,3-triazolobenzodiazepinones via tandem Ugi reaction/catalyst-free intramolecular azide–alkyne cycloaddition

• Maryna O. Mazur,
• Oleksii S. Zhelavskyi,
• Eugene M. Zviagin,
• Svitlana V. Shishkina,
• Vladimir I. Musatov,
• Maksim A. Kolosov,
• Elena H. Shvets,
• Anna Yu. Andryushchenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2021, 17, 678–687, doi:10.3762/bjoc.17.57

• products 6aba, 6aca and 6bba, based on aromatic amines, a higher temperature was required. In contrast to IAAC on terminal alkynes, the yields for the cyclization of internal alkynes were significantly lower due to the abovementioned difficulties with isolation and thermal degradation. Conclusion In

The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

• Itamar L. Gonçalves,
• Rafaela R. da Rosa,
• Vera L. Eifler-Lima and
• Aloir A. Merlo

Beilstein J. Org. Chem. 2020, 16, 175–184, doi:10.3762/bjoc.16.20

• and 22 only show thermal degradation above 300 °C, while thiourea 18c decomposed above 200 °C (Figure 4). Also, amides 20 and 22, which are isomers due to the change of the nitrogen and oxygen positioning in the isoxazole core, presented the same degradation behavior. Conclusion The results reported

Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation

• Andreas Boelke,
• Yulia A. Vlasenko,
• Mekhman S. Yusubov,
• Boris J. Nachtsheim and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2019, 15, 2311–2318, doi:10.3762/bjoc.15.223

• )cyclic iodanes. Albeit aryl-λ3-iodanes are viewed as safe and stable under ambient temperatures, systematic thermal degradation studies of hypervalent iodine reagents are still rare. In 1992 Varvoglis and co-workers investigated the thermal degradation of a variety of aryl iodine(III) dicarboxylates into

Continuous-flow retro-Diels–Alder reaction: an efficient method for the preparation of pyrimidinone derivatives

• Imane Nekkaa,
• Márta Palkó,
• István M. Mándity and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2018, 14, 318–324, doi:10.3762/bjoc.14.20

• –14 were identical with their literature data (Supporting Information File 1). The rDA reaction is basically a thermally-driven process. Consequently, by careful reaction parameter optimization, a balance should be found between the desired rDA cycloreversion reaction and the unwanted thermal

• degradation of the rDA product. The conversion and yield of a reaction under CF conditions is influenced directly by the residence time and reaction temperature, which are crucial determining factors in flow chemistry [18][19][20]. Thus, these two parameters were fine-tuned for all of the starting materials

Novel approach to hydroxy-group-containing porous organic polymers from bisphenol A

• Tao Wang,
• Yan-Chao Zhao,
• Li-Min Zhang,
• Yi Cui,
• Chang-Shan Zhang and
• Bao-Hang Han

Beilstein J. Org. Chem. 2017, 13, 2131–2137, doi:10.3762/bjoc.13.211

• thermal degradation for PPOPs until when heated up to 300 °C. According to the TGA result of BPA (Supporting Information File 1, Figure S2), the thermal degradation of BPA begins around 180 °C and the evolved products are mainly phenol with one or two benzene rings from investigations of thermal

• degradation of bisphenol A polycarbonate [28]. Investigation of the changes from methyl groups and aldehyde groups between monomers and polymers is carried out by means of FTIR spectroscopy. The FTIR spectra displayed (Figure 1 and Supporting Information File 1, Figure S3) that signal at 2970 cm−1 arised from

Adsorption of RNA on mineral surfaces and mineral precipitates

• Elisa Biondi,
• Yoshihiro Furukawa,
• Jun Kawai and
• Steven A. Benner

Beilstein J. Org. Chem. 2017, 13, 393–404, doi:10.3762/bjoc.13.42

• thermal degradation in aqueous solution. 18% denaturing PAGE of a 83-mer ssRNA incubated for 2 hours at 25, 37, 55, 75, and 95 °C, either free (left) or adsorbed to aragonite (right). Full length RNA and nucleotides in the sequence that are hot spots for degradation are indicated on the left. Adsorption

Extrusion – back to the future: Using an established technique to reform automated chemical synthesis

• Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 65–75, doi:10.3762/bjoc.13.9

• component in the mixture [45]. Furthermore, it was reported that batch heating also resulted in the thermal degradation of choline chloride:D-fructose DES due to the caramelisation of D-fructose [45]. TSE overcame the problems identified by batch heating. The residence time for the continuous extrusion of

• the DES components was determined to be 4–8 minutes on average, producing quantities of ca. 0.4 kg h−1 (value of Reline 200 collected per hour) of DES [44]. The reaction times in the formation of DESs was greatly decreased, and as a result, thermal degradation was avoided in those DESs containing D

Thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) and complexation with β-cyclodextrin

• Daniel I. Hădărugă,
• Mustafa Ünlüsayin,
• Alexandra T. Gruia,
• Cristina Birău (Mitroi),
• Gerlinde Rusu and
• Nicoleta G. Hădărugă

Beilstein J. Org. Chem. 2016, 12, 179–191, doi:10.3762/bjoc.12.20

• intermediates resulting from the oxidation of FAs are monohydroperoxides, hydroperoxy-epidioxides, as well as peroxy-, alkoxy-, and alkyl radicals [16]. Further thermal degradation or fragmentation of these intermediates leads to odor-active carbonyl compounds such as aldehydes, ketones, alcohols and esters

Self-assemblies of γ-CDs with pentablock copolymers PMA-PPO-PEO-PPO-PMA and endcapping via atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine

• Jing Lin,
• Tao Kong,
• Lin Ye,
• Ai-ying Zhang and
• Zeng-guo Feng

Beilstein J. Org. Chem. 2015, 11, 2267–2277, doi:10.3762/bjoc.11.247

• . As shown in Figure 8, the free γ-CD began to decompose at about 300 °C and the PEP100M at around 325 °C. Unlike either the pure γ-CD or PEP100M, the PEP100M10CD and PEP100M30CD samples underwent a two-step, thermal degradation process. The thermal weight loss at about 275 °C and 350 °C is attributed

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• reactions of tri- and tetrasubstituted olefins [42][46], cross-metathesis (CM) to afford trisubstituted olefins [44] and CM and RCM reactions of electron-withdrawing substituted olefins [45]. In comparison to the 1st generation, they show a generally higher stability towards thermal degradation [41][42][43

Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

• Shawna L. Balof,
• K. Owen Nix,
• Matthew S. Olliff,
• Sarah E. Roessler,
• Arpita Saha,
• Kevin B. Müller,
• Ulrich Behrens,
• Edward J. Valente and
• Hans-Jörg Schanz

Beilstein J. Org. Chem. 2015, 11, 1960–1972, doi:10.3762/bjoc.11.212

• ., a water molecule which also resulted in a significant stabilization of these activated species from thermal degradation. Since lowering the degree of protonation in H2ITap ligated Ru–alkylidene complexes has been demonstrated to improve the catalytic activity [62], it cannot be ruled out that the

Photo, thermal and chemical degradation of riboflavin

• Muhammad Ali Sheraz,
• Sadia Hafeez Kazi,
• Sofia Ahmed,
• Zubair Anwar and
• Iqbal Ahmad

Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208

• this field has been made and all those factors that affect the photo, thermal and chemical degradation of RF have been discussed. RF undergoes degradation through several mechanisms and an understanding of the mode of photo- and thermal degradation of RF may help in the stabilization of the vitamin. A

• general scheme for the photodegradation of RF is presented. Keywords: chemical degradation; degradation products; photodegradation; riboflavin; stability; thermal degradation; Review The study of photo, thermal and chemical degradation in the stability of drugs is one of the most concerned areas in the

• like dried silica to prevent moisture adsorption from the environment [73]. Thermal degradation of riboflavin RF is a heat stable compound and little information is available regarding its thermal degradation in aqueous solution. However, some degradation pathways and products have been reported for

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• for an almost infinite length of time. The isomers should have an appreciable resistance to fatigue (number of cycles without decomposition), with the possibility to carry out the cycle of write/erase several times, and should not cause thermal degradation or photochemical side-products. The two

Continuous preparation of carbon-nanotube-supported platinum catalysts in a flow reactor directly heated by electric current

• Alicja Schlange,
• Antonio Rodolfo dos Santos,
• Ulrich Kunz and
• Thomas Turek

Beilstein J. Org. Chem. 2011, 7, 1412–1420, doi:10.3762/bjoc.7.165

• CNTs starts to decompose at lower temperature. The thermal degradation of HNO3-treated CNTs in the temperature range between 150 to 350 °C is caused by the decomposition of the carboxylic groups attached to the surface during the nitric acid treatment. A weight loss of 4.69% in this temperature region

Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

• Yannick Borguet,
• Xavier Sauvage,
• Guillermo Zaragoza,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2010, 6, 1167–1173, doi:10.3762/bjoc.6.133

• the whole process through the use of a monomodal microwave reactor (Table 2, entry 7). Such a device is becoming increasingly popular in organic synthesis and has already been used as a convenient heating source for numerous ruthenium-catalyzed reactions [38]. Because thermal degradation of the