Investigation of cationic ring-opening polymerization of 2-oxazolines in the “green” solvent dihydrolevoglucosenone

• Solomiia Borova and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2023, 19, 217–230, doi:10.3762/bjoc.19.21

• potassium hydroxide tend to terminate at the 2-position. This results in the formation of POx containing a secondary amine and a cleavable ester terminal group [49]. Subsequent dehydration under conditions of MALDI-TOF mass spectrometry might lead to a dehydration, although this is speculative at this point

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

• structure was subsequently secured by preparation from 1 through Cope rearrangement [20] and through dehydration of elemol (7) with POCl3 in pyridine yielding 5 and β-elemene (8) (Scheme 3D) [45]. Compound 5 has also frequently been reported from natural sources especially after heat treatment of the sample

• catalytic hydrogenation to 27, dehydration to a mixture of alkenes (28) and hydrogenation to selinane (29) it was concluded that 11 was a selinane sesquiterpene alcohol (Scheme 9B) [75]. Four years later, based on NMR data Bhattacharyya and co-workers suggested a cis-ring junction for 11 [76], but a

• synthesis from β-eudesmol (30) through epoxidation to 31, dehydration to 32 and epoxide opening with LiAlH4 yielded (−)-11 (Scheme 9C) [77], contradicting this assignment. Notably, Šorm and co-workers noticed that 11 was racemic, because neither 11 nor any of its degradation products showed optical activity

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• unsaturated versions 1,4-dithiin (3) and 5,6-dihydro-1,4-dithiin (2, Scheme 4) [25]. However, more convenient synthetic procedures exist for the synthesis of these two basic heterocycles. For the synthesis of large amounts of 1,4-dithiin (3), this can be most conveniently achieved by a double dehydration of

• the commercially available 1,4-dithiane-2,5-diol (4) [26]. The diol 4 is commercially available in large quantities and is formally also a 1,4-dithiane derivative, but except for its dehydration to 1,4-dithiin, it is almost exclusively used as a source of mercapto acetaldehyde (of which it is a direct

• quantities from a limited number of suppliers. Oxidation and dehydration of 5 to the fully unsaturated ring system 6 is quite straightforward (especially compared to the same reactions on 1,4-dithiane (1)), and yields the useful building block 6. For the availability of the disulfone series of derivatives of

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• and final dehydration by Burgess reagent provided the total syntheses of magninoids A (104) and C (103, Scheme 8). Divergent total synthesis of crinipellins (Xie and Ding 2022) [53]: Crinipellins are highly congested tetraquinane natural products comprising 6–10 stereogenic centers, three of which are

Inclusion complexes of the steroid hormones 17β-estradiol and progesterone with β- and γ-cyclodextrin hosts: syntheses, X-ray structures, thermal analyses and API solubility enhancements

• Alexios I. Vicatos,
• Zakiena Hoossen and
• Mino R. Caira

Beilstein J. Org. Chem. 2022, 18, 1749–1762, doi:10.3762/bjoc.18.184

• correlate when comparing the results obtained from the TGA and DSC instruments, but the two methods did involve different sample configurations (samples in open pans vs crimped, vented pans). For all four complexes dehydration was initially observed, either as a multi- or single-step process, as confirmed

Cytochrome P450 monooxygenase-mediated tailoring of triterpenoids and steroids in plants

• Karan Malhotra and
• Jakob Franke

Beilstein J. Org. Chem. 2022, 18, 1289–1310, doi:10.3762/bjoc.18.135

• compound 0. This nucleophilic and basic intermediate is prone to dehydration (step 6), leading to the strongly electrophilic and oxidising key intermediate G, which is commonly known as compound I (cpd I). Although there has been a lot of debate regarding the exact structure and electronic properties of

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

• compound 2. The isopropenyl residue of the target compound 1 was assembled through a two-step sequence. The first one was the addition of an excess of methylmagnesium bromide to the ester 2, that completed the carbon skeleton. The second step was the pH-controlled regioselective dehydration of the tertiary

A one-pot electrochemical synthesis of 2-aminothiazoles from active methylene ketones and thioureas mediated by NH₄I

• Shang-Feng Yang,
• Pei Li,
• Zi-Lin Fang,
• Sen Liang,
• Hong-Yu Tian,
• Bao-Guo Sun,
• Kun Xu and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2022, 18, 1249–1255, doi:10.3762/bjoc.18.130

• dehydration to give the heterocyclic product 3. At the cathode, protons are reduced to release H2. Conclusion In conclusion, we have developed a one-pot electrochemical strategy for the synthesis of 2-amniothiazoles by the reaction of active methylene ketones with thioureas. The electrochemical synthesis was

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• dehydration of the resulting hydrate through short-patch distillation gave the desired vic-tricarbonyl compound 102. 3. α,β-Diketoesters as key intermediates Preussochromone E and F In a short and enantioselective total synthesis of preussochromone E (110) and F (109), Koert et al. used the complex vic

Synthesis of tryptophan-dehydrobutyrine diketopiperazine and biological activity of hangtaimycin and its co-metabolites

• Houchao Xu,
• Anne Wochele,
• Minghe Luo,
• Gregor Schnakenburg,
• Yuhui Sun,
• Heike Brötz-Oesterhelt and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 1159–1165, doi:10.3762/bjoc.18.120

• DBU is a common strategy for the dehydration of serine and threonine units in peptides [16], but unfortunately the acetylation of 10 failed. Interestingly, the direct treatment of 10 with LiClO4 and DBU under prolonged reaction times (3 days) resulted in the elimination of water. This reaction

New azodyrecins identified by a genome mining-directed reactivity-based screening

• Atina Rizkiya Choirunnisa,
• Kuga Arima,
• Yo Abe,
• Noritaka Kagaya,
• Kei Kudo,
• Hikaru Suenaga,
• Junko Hashimoto,
• Manabu Fujie,
• Noriyuki Satoh,
• Kazuo Shin-ya,
• Kenichi Matsuda and
• Toshiyuki Wakimoto

Beilstein J. Org. Chem. 2022, 18, 1017–1025, doi:10.3762/bjoc.18.102

• , their enzymatic basis has remained elusive except for the exo-olefin formation in valanimycin biosynthesis, which is mediated by the phosphorylation of a serine moiety by VlmJ and the subsequent dehydration by VlmK [33]. To obtain insights into the late-stage diversification mechanisms, we focused on

Molecular diversity of the base-promoted reaction of phenacylmalononitriles with dialkyl but-2-ynedioates

• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 991–998, doi:10.3762/bjoc.18.99

• exist in cis-position. Sequentially, nucleophilic addition of the amino group of intermediate F to the C–C double bond connecting the two alkoxycarbonyl groups in molecule 3 resulted in the formation of intermediate G. At last, the base-catalyzed dehydration and elimination of hydrocyanide gave the

Electroreductive coupling of 2-acylbenzoates with α,β-unsaturated carbonyl compounds: density functional theory study on product selectivity

• Naoki Kise and
• Toshihiko Sakurai

Beilstein J. Org. Chem. 2022, 18, 956–962, doi:10.3762/bjoc.18.95

• 6a could not be purified, it was treated with 1 M HCl/dioxane 1:1 at 25 °C for 1 h to give desilylated alcohol 7a in 78% yield (2 steps) as a mixture of two diastereomers (78:22 dr). Dehydration of compound 7a in refluxing toluene in the presence of cat. PPTS produced 2-cyanonaphthalene-1-ol (3a) in

• 1 M HCl without dehydration in refluxing cat. PPTS/toluene (Table 1, entries 2–4 and 7). From 5,6-dimethoxy substrate 1d, phthalide 4d was also formed together with naphthol 3d (Table 1, entry 4). In contrast, phthalides 4e and 4f were the sole products in the reactions of 6-methoxy and 4,5,6

• intramolecular addition of the anion D and subsequent O-trimethylsilylation of the resultant E produces intermediate 6 (path c). Desilylation of 6 with 1 M HCl and following dehydration of 7 affords product 3. On the other hand, O-trimethylsilylation of anion D forms N-(trimethylsilyl)ethenimine F and subsequent

Anti-inflammatory aromadendrane- and cadinane-type sesquiterpenoids from the South China Sea sponge Acanthella cavernosa

• Shou-Mao Shen,
• Qing Yang,
• Yi Zang,
• Jia Li,
• Xueting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 916–925, doi:10.3762/bjoc.18.91

• at C-7 and C-10 to give a pair of dihydroxy epimers 4 and 5. Compound 6 could be generated by the dehydration of 4/5 or by the multiple-step oxidation of M. Similarly, the plausible biosynthetic pathway of compound 7 could be proposed below. Multiple-step oxidation of N gave a phenolic sesquiterpene

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

• method was more efficient than the DCC coupling one. The similar treatment of alkyl 2-aminobenzyl(phenyl)phosphinates 53 and 63 gave 1-alkyl-2-phenyl-1,3-dihydrobenzo[d][1,2]azaphosphole 2-oxides 56 in 51–65% yield through the alkyl transfer from the O to the N atom followed by dehydration under heating

• similar alkyl transfer from the O to N atom followed by dehydration under heating (Scheme 11) [31]. Natchev prepared racemic and optically active ethyl 2-methyl-1,2-azaphospholidine-5-carboxylate 2-oxide (69) as cyclic analogue of the herbicide phosphinothricin (glufosinate, ᴅʟ-68) from ᴅʟ-, ᴅ-, and ʟ-2

Copper-catalyzed multicomponent reactions for the efficient synthesis of diverse spirotetrahydrocarbazoles

• Shao-Cong Zhan,
• Ren-Jie Fang,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 796–808, doi:10.3762/bjoc.18.80

• 3-substituted indole, which undergoes dehydration to form the key intermediate indole-based ortho-quinodimethanes (o-QDMs, A). In the meantime, the cyclic 1,3-diones and aromatic aldehyde undergo Knoevenagel condensation to afford the different kinds of dienophiles. Subsequently, the Diels–Alder

A trustworthy mechanochemical route to isocyanides

• Francesco Basoccu,
• Federico Cuccu,
• Federico Casti,
• Rita Mocci,
• Claudia Fattuoni and
• Andrea Porcheddu

Beilstein J. Org. Chem. 2022, 18, 732–737, doi:10.3762/bjoc.18.73

• does not respect the octet rule, is less favoured (Figure 1). The synthetic approaches to this core are multiple, but numerous drawbacks severely limit their output. Common pathways generally involve formamides; one of the most known is Ugi’s method [17] which is based on the dehydration of a primary

Sesquiterpenes from the soil-derived fungus Trichoderma citrinoviride PSU-SPSF346

• Wiriya Yaosanit,
• Vatcharin Rukachaisirikul,
• Souwalak Phongpaichit,
• Sita Preedanon and
• Jariya Sakayaroj

Beilstein J. Org. Chem. 2022, 18, 479–485, doi:10.3762/bjoc.18.50

• lactone moiety and demethylation, respectively (Figure 4). Subsequent dehydration would afford compound 2 with an α,β-unsaturated carboxylic acid moiety. Alternatively, the ring opening of compound 4 and demethylation of compound 5 would occur prior to the oxa-Michael reaction. Accordingly, the absolute

Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides

• Md Imran Hossain,
• Md Imdadul H. Khan,
• Seong Jong Kim and
• Hoang V. Le

Beilstein J. Org. Chem. 2022, 18, 446–458, doi:10.3762/bjoc.18.47

• Discussion The reason why we investigated the reaction under mild basic conditions was because nitrile oxides are often generated by dehalogenation of hydroximoyl chlorides in situ under basic conditions or by dehydration of nitroalkanes [30]. So we were wondering whether we could take advantage of that

A resorcin[4]arene hexameric capsule as a supramolecular catalyst in elimination and isomerization reactions

• Tommaso Lorenzetto,
• Fabrizio Fabris and
• Alessandro Scarso

Beilstein J. Org. Chem. 2022, 18, 337–349, doi:10.3762/bjoc.18.38

• , thus excluding a fundamental role of the cavity under such experimental conditions for carvone isomerization. Dehydration of 1,1-diphenylethanol to 1,1-diphenylethylene The dehydration reaction of 1,1-diphenylethanol to 1,1-diphenylethylene occurs with protonation at the oxygen atom of the reagent with

• protonation occurred preferentially on the alkene moiety. It is worth to note that the present dehydration reaction of 1,1-diphenylethanol with 16 occurs under mild experimental conditions with respect to recent examples in the literature operating with strong Brønsted and Lewis acids like sulfuric acid [57

• , tetrabutylammonium bromide (3) to act as a competitive guest for the cavity and acetic acid (4) to mimic just the Brønsted acidity of the capsule. Carbonyl–ene intramolecular cyclization of (S)-citronellal to the corresponding diastereoisomeric cyclic secondary alcohols. Dehydration reaction of 1,1-diphenylethanol

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• ligands (Figure 7a). The normally used analogous smaller-sized host was assembled with naphthalene-walled ligands, which had been used widely in mediating various reactions, including dehydration reaction [65], aza-Darzens reaction [66], and reductive amination [67], etc. [28]. The anionic cage host

Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• assigned as 1-alkyl-3,5,5-trimethyl-5,6-dihydro-1H-azepino[4,3,2-cd]indoles 8. The authors proposed that aza-Michael addition of 4-aminoindoles 7 to in situ generated mesityl oxide gives compound 9 which undergoes a regioselective intramolecular cyclization–dehydration sequence to furnish 8. In 2019, Zou

• [4,3,2-cd]indoles via indole C3 regioselective aza-Michael addition/cyclization/dehydration sequence. Indole C3 regioselective Pictet−Spengler reaction of 2-(1H-indol-4-yl)ethanamines. Indole C3 regioselective hydroindolation of cis-β-(α′,α′-dimethyl)-4′-methindolylstyrenes. Indole C3 regioselective

New efficient synthesis of polysubstituted 3,4-dihydroquinazolines and 4H-3,1-benzothiazines through a Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution sequence

• Long Zhao,
• Mao-Lin Yang,
• Min Liu and
• Ming-Wu Ding

Beilstein J. Org. Chem. 2022, 18, 286–292, doi:10.3762/bjoc.18.32

• of their derivatives [12][13][14][15][16][17][18][19][20][21][22]. For example (Scheme 1), a one-pot Tf2O-mediated assembly of amides, amines, and ketones provided 3,4-dihydroquinazolines in good yields via successive triflic anhydride-mediated amide dehydration, ketimine addition, and Pictet

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• of two isomeric 1,2-oxazoles (Scheme 2) [34][35]. In the first route, enaminone 3a–h and hydroxylamine gives intermediate A, which then removes one molecule of dimethylamine to form intermediate B. This is followed by intramolecular cyclization to intermediate C, and subsequent dehydration to

• generate the final products 4a–h. Alternatively, nucleophilic attack of hydroxylamine to the carbonyl carbon atom of the enone moiety forms intermediate D. The dehydration of the latter provides oxime E, which through the formation of intermediate F, should be capable to form final product VII. However, as

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• CPA 9 catalysis, the intermediate I-22 is converted to I-23, which after dehydration forms the desired enantioenriched products, polysubstituted 4-arylquinolines 79 in high yield (up to 94%) with good to excellent enantioselectivities (up to 97% ee, Scheme 26). The chiral phosphoric acid catalyst