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

• single-cis conformation. Ando and co-workers prepared the symmetrical 1,4-dithiane 41 (Scheme 9a) [55], and amply illustrated the concept by reacting it in a [4 + 2] cycloaddition with a highly reactive diazo dienophile (Cookson’s reagent or 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD)) to afford the bis

A novel bis-triazole scaffold accessed via two tandem [3 + 2] cycloaddition events including an uncatalyzed, room temperature azide–alkyne click reaction

• Ksenia Malkova,
• Andrey Bubyrev,
• Vasilisa Krivovicheva,
• Dmitry Dar’in,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1636–1641, doi:10.3762/bjoc.18.175

• scaffolds. Recently, we reported a novel, metal-free synthesis of 1,5-disubstituted 1,2,3-triazoles via a three-component reaction of α-acetyl-α-diazomethanesulfonamide (1) with aldehydes and amines [4]. The reaction proceeded, presumably, through the formation of the initial 1,2,3-triazoline adduct 2 [5

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• of the imine intermediate produces the intermediate enamine 13. The 1,3-dipolar cycloaddition of enamine 13 with azide produces intermediate 1,2,3-triazoline 14. In continuation, a ring-opening process is promoted by acetic acid to afford the intermediate 16. Afterward, triazene intermediate 17 was

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• ], 6,7-dihydro-6-oxo-5H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazine [17], 1,2,4-triazino[5,6-b]indole [18], 1,3,4-thiadiazoline [19], 1,3,4-oxadiazoline [19], 1,2,4-triazoline [19], 3-mercapto-1H-1,2,4-triazole [20], 1,3,4-oxadiazole-2(3H)-thione [20], 4-amino-5-mercapto-4H-1,2,4-triazole [20], and 1,2,4

Catalyst-free synthesis of 4-acyl-NH-1,2,3-triazoles by water-mediated cycloaddition reactions of enaminones and tosyl azide

• Lu Yang,
• Yuwei Wu,
• Yiming Yang,
• Chengping Wen and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2018, 14, 2348–2353, doi:10.3762/bjoc.14.210

• -triazoline 4 which couples to water by strong hydrogen bond effect [51]. The presence of the hydrogen bonds may promote the elimination of the amino group and the acidic C–H bond at the α-position of the acyl group, which affords N-tosyl-1,2,3-triazole 5. Under the present reaction conditions, the

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• -triazoline-3,5-dione (158) gave the cycloadducts 159 and 160 via the cycloheptatriene form. However, usually the norcaradiene type product 161 observed with cycloheptatrienes was not formed (Scheme 27). 3. Chemistry of 2,3-benzotropone (12) 3.1. Synthesis of 2,3-benzotropone (12) Several procedures relating

A new synthetic access to 2-N-(glycosyl)thiosemicarbazides from 3-N-(glycosyl)oxadiazolinethiones and the regioselectivity of the glycosylation of their oxadiazolinethione precursors

• El Sayed H. El Ashry,
• El Sayed H. El Tamany,
• Mohy El Din Abdel Fattah,
• Mohamed R. E. Aly,
• Ahmed T. A. Boraei and
• Axel Duerkop

Beilstein J. Org. Chem. 2013, 9, 135–146, doi:10.3762/bjoc.9.16

• respective thiosemicarbazides. Surprisingly, the formation of the galactosyl-1,2,4-triazoline-3-thione from the galactosyl-1,3,4-oxadiazole-2(3H)-thione was discovered for the first time. This is a new method for the conversion of an 1,3,4-oxadiazole-2(3H)-thione ring into a 1,2,4-triazoline-3-thione

• , because formerly, only conversions of 1,3,4-oxadiazolethione (by reaction of hydrazine hydrate) to 4-amino-1,2,4-triazolinethiones were reported [38][39][40]. The products of the new reactions are verified by the X-ray single-crystal analysis of the galactosyl-1,2,4-triazoline-3-thione, and a

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• affinity of 47a, can thus be explained by the gain of aromaticity during electrophilic attack. The same line of arguments can be used to rationalize the higher nucleophilicities and basicities of the triazoline derivatives 45b and 47b, respectively [107]. As the unsaturated carbenes 49a and 49b have

Synthesis of cross-conjugated trienes by rhodium-catalyzed dimerization of monosubstituted allenes

• Tomoya Miura,
• Tsuneaki Biyajima,
• Takeharu Toyoshima and
• Masahiro Murakami

Beilstein J. Org. Chem. 2011, 7, 578–581, doi:10.3762/bjoc.7.67

• dimerization reaction, in contrast to the nickel-catalyzed reaction [18][19]. Next, we examined the consecutive double [4 + 2] cycloaddition reaction of the cross-conjugated trienes obtained in the present study. Triene 3a was treated with 4-phenyl-1,2,4-triazoline-3,5-dione (4, PTAD), a highly reactive

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• shift the equilibrium to the norcaradiene 4b side, while electron donating substituents, such as –OR, –NR2 favor the cycloheptatriene 4a structure. It has been shown that singlet oxygen and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) are sufficiently reactive to intervene in the cycloheptatriene

Brønsted acid-promoted azide–olefin [3 + 2] cycloadditions for the preparation of contiguous aminopolyols: The importance of disiloxane ring size to a diastereoselective, bidirectional approach to zwittermicin A

• Hubert Muchalski,
• Ki Bum Hong and
• Jeffrey N. Johnston

Beilstein J. Org. Chem. 2010, 6, 1206–1210, doi:10.3762/bjoc.6.138

• diol. This development provides a basis for a stereocontrolled approach to the aminopolyol core of (−)-zwittermicin A using a bidirectional synthesis strategy. Keywords: azide; bidirectional synthesis; cycloaddition; dialkoxydisiloxane; TIPDS; triazoline; triflic acid; zwittermicin A; Introduction

• arise from the acid-promoted fragmentation of 2,3-anti / 2’,3’-anti bis(triazoline) 3 (Scheme 1). Compound 3 would be assembled in a sequential substrate-controlled intermolecular cycloaddition between imide 4 and benzyl azide. We envisioned that the facial discrimination could be provided by a large

• (NOESY, see Supporting Information File 1). Although the overall yield was satisfactory, purification of the desired 2,3-anti / 2’,3’-anti diastereomer 10a was tedious. We then turned our attention to triflic acid-promoted triazoline formation. When imide 5 was reacted with BnN3 in the presence of

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• gives rise to complex reaction mixtures due to the possibility of nitrene insertion. Cycloaddition of phenyl azide, however, to the unsaturated carbonyl 41 was readily accomplished to give triazoline 42 in 56% yield (Scheme 10) [53][54][55]. According to this scheme, the allylic alcohol 38 was oxidized

• with pyridinium dichromate and reacted with methylthiophenyl azide [56] to give the triazoline 40 derived from attack of the reagent from the concave face of the molecule with high diastereoselectivity (Scheme 11). The electronic effect or the α-methoxy group, as well as shielding of the α-face of the

• both this methoxy group and the one at the ring junction. Finally, the nitrogen of the lactam is located in the bridgehead position of a [3.3.0] bicycle resulting in poor delocalization into the adjacent carbonyl. A Barton deoxygenation gave compound 43, which was irradiated to decompose the triazoline