Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

• Xiaofeng Zhang,
• Xiaoming Ma and
• Wei Zhang

Beilstein J. Org. Chem. 2023, 19, 1677–1693, doi:10.3762/bjoc.19.123

• maleimides in MeCN at 110 °C for 6 h afforded the corresponding monocycloaddition compounds followed by acylation to yield intermediates 22. The subsequent sequential Staudinger/aza-Wittig reaction of intermediates 22 gave products 23a–g in 48–75% yields with 5:1 to 6:1 dr (Scheme 14). This one-pot reaction

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• through an intramolecular aza-Wittig reaction, yielding cyclopropane-fused 2-quinolones [2]. A nitro group not only activates substrates and stabilizes the α-anion as an electron-withdrawing group but also acts as a nucleophile, electrophile, and leaving group, exhibiting diverse reactivities [3]. For

Facile access to 3-sulfonylquinolines via Knoevenagel condensation/aza-Wittig reaction cascade involving ortho-azidobenzaldehydes and β-ketosulfonamides and sulfones

• Ksenia Malkova,
• Andrey Bubyrev,
• Stanislav Kalinin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2023, 19, 800–807, doi:10.3762/bjoc.19.60

• have developed a new convenient protocol for the synthesis of 3-sulfonyl-substituted quinolines (sulfonamides and sulfones). The approach is based on a Knoevenagel condensation/aza-Wittig reaction cascade involving o-azidobenzaldehydes and ketosulfonamides or ketosulfones as key building blocks. The

• protocol is appropriate for both ketosulfonyl reagents and α-sulfonyl-substituted alkyl acetates providing the target quinoline derivatives in good to excellent yields. Keywords: aza-Wittig reaction; azides; cyclocondensation; quinolones; sulfonamides; Introduction The quinoline scaffold has a wide

• , the method for the synthesis of 3-acyl-substituted quinolines from o-azidobenzaldehydes and 1,3-dicarbonyl compounds was reported [70][71] (Figure 2a). A combination of Knoevenagel condensation and aza-Wittig reaction allowed to build up target products in high yields. In case of [70], the procedure

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

• /addition/nucleophilic substitution reactions. Keywords: aza-Wittig reaction; 3,4-dihydroquinazoline; 4H-3,1-benzothiazine; nucleophilic substitution; Passerini reaction; Staudinger reaction; Introduction The chemistry of 3,4-dihydroquinazolines and 4H-3,1-benzothiazines is of constant interest owing to

• reaction has also been utilized widely in preparation of various heterocycles under mild neutral conditions [30][31][32]. Recently we have reported the synthesis of 3H-2-benzoxepin-1-ones, 4H-3,1-benzoxazines and oxazoles by combination of a Passerini with an intramolecular aza-Wittig reaction [33][34][35

• ]. Continuing our interest in the synthesis of N-heterocycles via the aza-Wittig reaction and multicomponent reactions [36][37][38], we wish to report herein a facile synthesis of polysubstituted 3,4-dihydroquinazolines and 4H-3,1-benzothiazines via sequential Passerini/Staudinger/aza-Wittig/addition

Total synthesis of pyrrolo[2,3-c]quinoline alkaloid: trigonoine B

• Takashi Nishiyama,
• Erina Hamada,
• Daishi Ishii,
• Yuuto Kihara,
• Nanase Choshi,
• Natsumi Nakanishi,
• Mari Murakami,
• Kimiko Taninaka,
• Noriyuki Hatae and
• Tominari Choshi

Beilstein J. Org. Chem. 2021, 17, 730–736, doi:10.3762/bjoc.17.62

• . Consequently, we decided to develop a new synthetic strategy for the preparation of trigonoine B (1). Carbodiimides are valuable synthetic intermediates that can be obtained by an aza-Wittig reaction of isocyanates with iminophosphoranes or by dehydration of urea [26]. Molina et al. previously reported the

• synthesis of 2-aminopyridine derivatives through an electrocyclization of conjugated carbodiimides derived from an aza-Wittig reaction of iminophosphoranes and isocyanates [27]. Hibino and co-workers also achieved the preparation of mutagenic amino-α-carbolines (2-amino-9H-pyrido[2,3-b]indole, AαC) and

• MeAαC by the electrocyclization of 3-alkenyl-2-carbodiimidoindole derivatives obtained by an aza-Wittig reaction of indol-2-yl-iminophosphoranes and isocyanates [28]. In this work, we report the first total synthesis of trigonoine B (1) involving the construction of a pyrrolo[2,3-c]quinoline framework

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• aza-Wittig reaction, it is regenerated as a byproduct, and thus can participate directly in another reaction cycle. More than 25 years before Huang’s research group made their first report regarding arsine catalysis [10], Tod W. Campbell and colleagues took advantage of this fact and reported a single

• example of a catalytic aza-Wittig reaction as part of their research on phosphine oxide-catalyzed carbodiimide synthesis (Scheme 13) [30]. In their reaction they used phosphine oxide 40 as the catalyst in the reaction between diisocyanate 41 and benzaldehyde (42, 2 equivalents) to form diimine 43 and

• materials (Scheme 19) [37]. For example, reactions of carboxylic acids 71 with acid chlorides 72 to generate the corresponding carboxylic acid anhydride in situ afforded 4H-benzo[d][1,3]-oxazin-4-ones 73. In these reactions, 1 was used as the catalyst for the aza-Wittig reaction and copper triflate was used

Direct access to pyrido/pyrrolo[2,1-b]quinazolin-9(1H)-ones through silver-mediated intramolecular alkyne hydroamination reactions

• Hengshuai Wang,
• Shengchao Jiao,
• Kerong Chen,
• Xu Zhang,
• Linxiang Zhao,
• Dan Liu,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2015, 11, 416–424, doi:10.3762/bjoc.11.47

• -insertion reaction [7], the cycloaddition of anthranilic acid iminoketene to a methyl butyrolactam through a sulfinamide anhydride intermediate [9], the intramolecular aza-Wittig reaction with an azide substrate [10], and the cycloaddition of anthranilamide [11]. For the synthesis of vasicinone (5

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• group has developed the synthesis of D-glucopyranose-derived counterparts of compounds 25 and 26 [73]. The formation of an intermediate imine from a sugar azide and an aldehyde by Staudinger/aza-Wittig reaction was the key step of the synthesis. 2. The Kabachnik–Fields reaction The Kabachnik–Fields

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• reaction of dihydrooxepine 325 (see Scheme 38) to access vinylcyclopropane carbaldehyde 326, which was in situ converted into the corresponding imine 327 using an aza-Wittig reaction. Subsequent vinylcyclopropane carbimine–dihydroazepine rearrangement furnished cyclic 328 in excellent yield. Conclusion The

One-pot sequential synthesis of isocyanates and urea derivatives via a microwave-assisted Staudinger–aza-Wittig reaction

• Diego Carnaroglio,
• Katia Martina,
• Giovanni Palmisano,
• Andrea Penoni,
• Claudia Domini and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2013, 9, 2378–2386, doi:10.3762/bjoc.9.274

• halides and primary or secondary amines has been developed. The synthetic pathway combines nucleophilic substitutions and a Staudinger–aza-Wittig reaction in the presence of polymer-bound diphenylphosphine under 14 bar of CO2 pressure and has been performed in a one-pot two-step process. The protocol has

• : isocyanates; microwave-assisted reaction; one-pot reaction; tandem Staudinger–aza-Wittig reaction; urea derivatives; Introduction The industrial and commercial impact of isocyanates (R–NCO) is steadily growing. In particular, the polyurethane output has undergone yearly increases of 5% over the last decade

• volatile, solid and supported reagents. In summary, we herein report an optimized protocol for a MW-assisted Staudinger–aza-Wittig reaction with polymer-bound diphenylphosphine (PS-PPh2) in a CO2 atmosphere. The study also aimed to prepare a series of symmetric and asymmetric alkyl/aryl urea derivatives in

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• starting materials, via a Staudinger–aza-Wittig reaction gave amine 237 as a mixture of four diastereoisomers. Conversion into 4-oxido-isoquinolinium betaine 238 could be achieved by an acid-catalyzed methanol extrusion and isomerization. Betaine 238 served as the substrate for the following 1,3-aza

Facile synthesis of benzothiadiazine 1,1-dioxides, a precursor of RSV inhibitors, by tandem amidation/intramolecular aza-Wittig reaction

• Krishna C. Majumdar and
• Sintu Ganai

Beilstein J. Org. Chem. 2013, 9, 503–509, doi:10.3762/bjoc.9.54

• -dioxides through an intramolecular aza-Wittig reaction. The reaction was found to be general through the synthesis of a number of benzothiadiazine 1,1-dioxides. Acid-catalyzed hydrolysis of 3-ethoxy-1,2,4-benzothiadiazine 1,1-dioxides furnished the 2-substituted benzothiadiazine-3-one 1,1-dioxides in good

• yields and high purity, which is the core moiety of RSV inhibitors. Keywords: benzothiadiazine-3-one 1,1-dioxide; 3-ethoxy-1,2,4-benzothiadiazine 1,1-dioxide; intramolecular aza-Wittig reaction; sultam; Introduction Sultams have gained popularity in the scientific community especially among synthetic

• derivatives have been reported [25][26][27][28][29][30][31][32], the development of a simpler method for the synthesis of the 1,2,4-benzothiadiazine 1,1-dioxide moiety is still desirable because of their biological significance. The aza-Wittig reaction is employed for the construction of C=N, N=N and S=N

Parallel and four-step synthesis of natural-product-inspired scaffolds through modular assembly and divergent cyclization

• Hiroki Oguri,
• Haruki Mizoguchi,
• Hideaki Oikawa,
• Aki Ishiyama,
• Masato Iwatsuki,
• Kazuhiko Otoguro and
• Satoshi Ōmura

Beilstein J. Org. Chem. 2012, 8, 930–940, doi:10.3762/bjoc.8.105

• and 4 (Scheme 2), as reported previously [22]. Due to the instability of the corresponding amine building block bearing the indole unit, azide 27 was employed as a precursor. Staudinger/aza-Wittig reaction [43] of 27 and 20 and subsequent condensation with 6 and 21 afforded the peptidyl product 28

The application of a monolithic triphenylphosphine reagent for conducting Appel reactions in flow microreactors

• Kimberley A. Roper,
• Heiko Lange,
• Anastasios Polyzos,
• Malcolm B. Berry,
• Ian R. Baxendale and
• Steven V. Ley

Beilstein J. Org. Chem. 2011, 7, 1648–1655, doi:10.3762/bjoc.7.194

• interest in using monolithic supports to facilitate key chemical transformations [20][21][22][23][24][25][26][27][28][29][30][31]. We recently reported on the development of a new monolithic triphenylphosphine reagent and its use in the Staudinger aza-Wittig reaction in flow [32][33]. Here we discuss the

A facile synthesis and fungicidal activities of 2-(alkylamino)-5,6-dimethylthieno[2,3-d]pyrimidin- 4(3H)-ones

• Yang-Gen Hu,
• Ai-Hua Zheng,
• Xu-Zhi Ruan and
• Ming-Wu Ding

Beilstein J. Org. Chem. 2008, 4, No. 49, doi:10.3762/bjoc.4.49

• activities against six kinds of fungi. Keywords: 2-(alkylamino)-5,6-dimethylthieno[2,3-d]pyrimidin-4(3H)-one; aza-Wittig reaction; fungicidal activity; synthesis; Introduction Over the past ten years, aza-Wittig reactions of functionalized iminophosphoranes with isocyanates have been applied to produce

• interested in the synthesis of a series of new heterocyclic compounds via aza-Wittig reaction of α- or β-(ethoxycarbonyl)-substituted iminophosphoranes with aromatic isocyanates and subsequent reaction with various nucleophiles under mild conditions [11][12][13][14]. Herein we wish to report an efficient