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

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• to good yield of 53–99% with an ee of 74–93% [54]. Liu et al. accomplished a catalytic cascade aza-Michael–Henry-dehydration protocol for the preparation of chiral 3-nitro-1,2-dihydroquinolines 83 from the reaction of N-protected aminobenzaldehydes 80 with substituted nitroolefins 81 by using

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• 64 (Figure 14b) [20][21]. The other enzyme believed to catalyze an α-ketol rearrangement is AuaG, which is a monooxygenase that uses FAD and molecular oxygen to convert aurachin C (66) to 69 (Figure 14c) [22]. Subsequent reduction and dehydration by AuaH produces aurachin B (71). While the above are

• hypothesized by several groups that one could be the biological precursor of the other by means of a reversible hydration–rearrangement–dehydration sequence (Figure 16a) [24][25][26]. The presence of the diazo group in intermediates 78 and 79 is noteworthy in that this functional group has not yet been

• demonstrated to be compatible with an α-ketol rearrangement. To test the feasibility of their hypothesis, Kawamura et al. subjected 80 to basic (Cs2CO3 or K2CO3) and acidic (TsOH) conditions [27]. While TsOH led only to dehydration product 81, the bases exclusively generated 82 as the result of an α-ketol

Cryogels: recent applications in 3D-bioprinting, injectable cryogels, drug delivery, and wound healing

• Luke O. Jones,
• Leah Williams,
• Tasmin Boam,
• Martin Kalmet,
• Chidubem Oguike and
• Fiona L. Hatton

Beilstein J. Org. Chem. 2021, 17, 2553–2569, doi:10.3762/bjoc.17.171

• mechanical integrity [5][12][13][60]. Possessing shape memory allows for dehydration and storing; rehydration before use restores their original shape [37][60]. Here, we discuss emerging areas for cryogel application, including recent advancements in the use of cryogels in 3D printing, injectable cryogels

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

• Robin Klintworth,
• Garreth L. Morgans,
• Stefania M. Scalzullo,
• Charles B. de Koning,
• Willem A. L. van Otterlo and
• Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

• -trig interactions of both the enol nucleophile and the ketone in the transient intermediate 21 bring about formation of the new five-membered ring intermediate 22. Finally, acid-induced dehydration of 22 completes the formation of the pyrrole ring, resulting in conversion into the dihydropyrrolizine

Isolation and characterization of new phenolic siderophores with antimicrobial properties from Pseudomonas sp. UIAU-6B

• Emmanuel T. Oluwabusola,
• Olusoji O. Adebisi,
• Fernando Reyes,
• Kojo S. Acquah,
• Mercedes De La Cruz,
• Larry L. Mweetwa,
• Joy E. Rajakulendran,
• Digby F. Warner,
• Deng Hai,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2021, 17, 2390–2398, doi:10.3762/bjoc.17.156

• -thioester intermediate followed by dehydration [44]. The incorporation of the decarboxylated phenylalanine by a nucleophilic unit to the intermediate salimethyloxazolinyl-thioester resulted in the formation of compound 5 without a rearrangement to isooxazolidinone owing to lack of N–OH in the phenylalanine

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• between alcohol and carbonyl groups (path a) or by hemiketal formation (path b). Thus, the chloride ion attacks from the frontside, producing syn-addition molecules that, upon dehydration, formed furan rings. Later they had reported similar mercuration of arylacetylenes to synthesize a broad spectrum of

• cyclization of secondary and tertiary l-alkynyl-2,3-epoxyalcohols 131a [94]. This is an example of a Hg(II)-salt-catalyzed rearrangement of 1-alkynyl-2,3-epoxy alcohols to substituted furans. The furan 133a was formed by dehydration of intermediate 132a through the corresponding oxonium cation. When R3 is an

• alkyl group, direct dehydration was not possible because of blocking. Later they reported a similar transformation of thiiranes to provide a wide variety of substituted thiophenes. They had synthesized substituted thiophenes 133b starting from thiiranes 131b via cyclization utilizing the catalytic

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• although they are classified in other categories that are also appropriate. Takai, Kuninobu, and their research group used an indium catalyst to synthesize polycyclic aromatic compounds via a reductive-dehydration intramolecular cycloaromatization [51], which is a Bradsher-type reaction. The authors

• procedure involving the cyclization of 2-arylmethylbenzoic acid 85b with triflic acid, followed by a NaBH4-mediated reductive dehydration. Some representative examples included anthracenes 86a–g. For those interested, the cyclodehydration was also extended to 2-(arylmethyl)naphthaldehydes and 2-(arylmethyl

• brominated naphthalene 153 with PhLi yielded compound 154, which collapsed to naphthotriyne 155 at elevated temperatures. Sequential addition of furan generated the trisadduct 156. Then, dibenz[a,c]anthracene 158 was obtained in good yield (86%) in two steps by hydrogenation of 156 and further dehydration of