(E,Z)-1,1,1,4,4,4-Hexafluorobut-2-enes: hydrofluoroolefins halogenation/dehydrohalogenation cascade to reach new fluorinated allene

• Nataliia V. Kirij,
• Andrey A. Filatov,
• Yurii L. Yagupolskii,
• Sheng Peng and
• Lee Sprague

Beilstein J. Org. Chem. 2024, 20, 452–459, doi:10.3762/bjoc.20.40

• -1,1,1,4,4,4-hexafluorobut-2-enes have been investigated. A simple, one-pot procedure for the preparation of a new allene (1,1,4,4,4-pentafluorobuta-1,2-diene) and some of its transformations is presented. Keywords: allenes; dehydrohalogenation; halogenation; 1,1,1,4,4,4-hexafluorobut-2-enes; isomerization

• showed a mixture of stereoisomers with a 2:1 ratio. The dehydrohalogenation reaction of 2-chloro-3-iodo-1,1,1,4,4,4-hexafluorobutane (5) was studied. Like the dehydrobromination of alkane 2, the reaction of compound 5 with 1.3 equivalents of KOH in water in the presence of 5 mol % of Bu4NBr was carried

• -hexafluorobutanes. Dehydrohalogenation of the obtained butanes leads to the formation of a number of bistrifluoromethyl-containing haloolefins, which are widely used in subsequent transformations. Based on bromoolefins 3a,b, a new polyfluoro-containing allene 11 was synthesized and its reactions with bromine and

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• alcohol 64. The formation of the double bond from alcohol 64 proved to be problematic, thus, replacement of the hydroxy group by iodine [47] followed by dehydrohalogenation using an excess of KF afforded methyl combretastatin D-2 (28) in 87% yield after two steps (Scheme 11). The authors also described a

Fritsch–Buttenberg–Wiechell rearrangement of magnesium alkylidene carbenoids leading to the formation of alkynes

• Tsutomu Kimura,
• Koto Sekiguchi,
• Akane Ando and
• Aki Imafuji

Beilstein J. Org. Chem. 2021, 17, 1352–1359, doi:10.3762/bjoc.17.94

• Sonogashira coupling reaction with organic halides. The dehydrohalogenation of gem-dihaloalkanes, vic-dihaloalkanes, and haloalkenes with strong bases is often used for the synthesis of alkynes [2]. An alternative strategy for the synthesis of alkynes is the conversion of carbonyl compounds through one-carbon

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• were increased when potassium fluoride and 18-crown-6 were added to the reaction mixture [20]. Dehydrohalogenation of dichlorodifluoromethane under phase-transfer catalysis: Difluorocarbene can be generated from chlorodifluoromethane by phase-transfer catalysis (PTC) through the reaction with NaOH or

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

• prepared by reacting α-tetralone (171) with ethyl orthoformate in the presence of an acid catalyst. Subsequent successive reactions are dihalocarbene addition to enolether 172, ring expansion of the adduct 173 to halocycloheptadienone 168, and dehydrohalogenation of 168 with lithium chloride. Later

Electrochemically modified Corey–Fuchs reaction for the synthesis of arylalkynes. The case of 2-(2,2-dibromovinyl)naphthalene

• Fabiana Pandolfi,
• Isabella Chiarotto and
• Marta Feroci

Beilstein J. Org. Chem. 2018, 14, 891–899, doi:10.3762/bjoc.14.76

• confirm the present interest in the chemistry of terminal alkynes, e.g., in the synthesis of sulfinamides and isothiazoles [4], 1,3-enynes [5], α-monosubstituted propargylamines [6], 2-substituted pyrazolo[5,1-a]isoquinolines [7], etc. Terminal alkynes can be prepared by dehydrohalogenation of vicinal

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• ]. Vinylphosphonium salt can also be synthesized by dehydrohalogenation of α-bromoethylphosphonium bromide 13 in the presence of lithium bromide in anhydrous dimethylformamide (Scheme 10). α-Bromoethylphosphonium salt 13 was obtained according to the three-step procedure, starting from the alkylation of

• -phenoxyethyltriphenylphosphonium bromide. β-Elimination of phenol from β-phenoxyethylphosphonium salts in an alkaline environment. Synthesis and subsequent dehydrohalogenation of α-bromoethylphosphonium bromide. Synthesis of tributylvinylphosphonium iodides via Peterson-type olefination of α-trimethylsilylphosphonium ylides with

Isoxazole derivatives as new nitric oxide elicitors in plants

• Anca Oancea,
• Emilian Georgescu,
• Florentina Georgescu,
• Alina Nicolescu,
• Elena Iulia Oprita,
• Catalina Tudora,
• Lucian Vladulescu,
• Marius-Constantin Vladulescu,
• Florin Oancea and
• Calin Deleanu

Beilstein J. Org. Chem. 2017, 13, 659–664, doi:10.3762/bjoc.13.65

• situ by the oxidative dehydrogenation of aldoximes in the presence of various oxidants [26][27][28][29], or by the dehydrohalogenation of hydroxyiminoyl halides promoted by organic or inorganic bases [30][31][32]. A less used synthetic procedure involves the oxidative dehydration of primary nitro

p-Nitrophenyl carbonate promoted ring-opening reactions of DBU and DBN affording lactam carbamates

• Madhuri Vangala and
• Ganesh P Shinde

Beilstein J. Org. Chem. 2016, 12, 2086–2092, doi:10.3762/bjoc.12.197

• unveiled their ability to act as C and N nucleophiles [5][6][7][8]. In 1981, McCoy and Mal first isolated an adduct of DBU with dimethyl 1-chloro-3-methyl cyclopropane-1,2-dicarboxylate during the dehydrohalogenation of halocyclopropanes [9]. In 1993, Bertrand and co-workers, showed that DBU and DBN act as

• promote dehydrohalogenation reactions, we turned our attention to halogenated alcohols. Thus, the p-nitrophenyl carbonate of 10-bromo-1-decanol 14a was reacted with DBN at 60 °C for 1 h affording a single polar spot on TLC. To our surprise, the 1H NMR spectrum showed the existence of two compounds with

Superoxide chemistry revisited: synthesis of tetrachloro-substituted methylenenortricyclenes

• Basavaraj M. Budanur and
• Faiz Ahmed Khan

Beilstein J. Org. Chem. 2014, 10, 2531–2538, doi:10.3762/bjoc.10.264

• . Keywords: BHT; dehydrohalogenation/rearrangement; Friedel–Crafts acylation; methylenenortricyclene; superoxide ion; Introduction The chemistry of the superoxide ion (O2−·) has been a subject of growing interest because of its presence in all aerobic organisms as a respiratory intermediate [1][2][3][4][5

• ) adducts of pentachloro-5-methylcyclopentadiene 1 and styrenes, by concurrent dehydrohalogenation and rearrangement reactions, starting from the commercially available inexpensive reagent potassium superoxide. Results and Discussion We have successfully utilized polyhalogenated bicyclic compounds for the

• (path A) or the direct dehydrohalogenation (path B) [47] (Scheme 4). We ruled out path A based on our observation that even after adding BHT, the reaction underwent smoothly. The second step involved the deprotonation of a benzylic proton by the superoxide ion [48]. The resulting benzylic anion I

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

• Mikko Passiniemi and
• Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

• the dehydrohalogenation of the phosphonium salt [103]. These complexes react with carbonyl compounds differently. Addition reactions of other ylides to 1, proceeded with little or no racemization of 1. The E/Z-ratio of the reaction was 1:13 favouring the Z-adduct 66. In comparison to Beaulieu’s

Aryl nitrile oxide cycloaddition reactions in the presence of pinacol boronic acid ester

• Sarah L. Harding,
• Sebastian M. Marcuccio and
• G. Paul Savage

Beilstein J. Org. Chem. 2012, 8, 606–612, doi:10.3762/bjoc.8.67

• nitrile oxides involves the dehydration of primary nitro compounds [21]. Aryl nitrile oxides are more commonly prepared by chlorination of aldoximes followed by dehydrohalogenation of the resulting hydroximoyl chlorides, or by direct oxidative dehydrogenation of the aldoximes (Scheme 2) [17]. While the

• halogenation–dehydrohalogenation process is most common, several methods involving direct oxidative dehydrogenation of aldoximes have been reported, including the use of lead tetraacetate [22][23], mercury(II) acetate [24], hypervalent iodine [25][26], and manganese(IV) oxide [27]. We were interested in

• ) or generated in situ by dehydrohalogenation of a preformed hydroximoyl chloride. This is presumably to avoid the competing oxidative side reactions that would be expected at the boronate ester if the nitrile oxide were generated oxidatively from the aldoxime [32]. The same thermodynamic bias

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• et al. using a double dehydrohalogenation of 1,2-dibromo-4,5-epoxycyclohexane [38][53], but is also accessible by epoxidation of Dewar benzene followed by photolytic or thermal ring expansion [54]. The molecular structure of the 2-tert-butoxycarbonyl oxepine showed a boat configuration with bow (α

Synthesis of novel 5-alkyl/aryl/heteroaryl substituted diethyl 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates by aziridine ring expansion of 2-[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters

• Satish S. More,
• T. Krishna Mohan,
• Y. Sateesh Kumar,
• U. K. Syam Kumar and
• Navin B. Patel

Beilstein J. Org. Chem. 2011, 7, 831–838, doi:10.3762/bjoc.7.95

• reactions led to various by-products probably as a result of protonation and dehydrohalogenation of the presumed intermediates [28] (Scheme 1). Junjappa and co-workers were successful in iodide ion mediated ring expansion of N-vinylaziridine N,S-acetals containing cyano- and ester groups on the β-carbon and

• quantitative yields, either by reduction with sodium borohydride, or by catalytic hydrogenation using platinum on carbon [33][34]. The pyrrolines can be aromatized either by a two step procedure (i) NBS bromination and (ii) dehydrohalogenation in basic medium [35][36][37], or by dehydrogenation with Pd/C [38

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• also employed in a similar flow system for the asymmetric α-chlorination of acid chlorides (Scheme 7) [31][32]. This cinchona alkaloid derivative served the dual purpose of dehydrohalogenation and asymmetric induction, and was found to be reusable at least up to 100 times, after regeneration each time

Shape- persistent macrocycle with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure

• Sigurd Höger,
• Jill Weber,
• Andreas Leppert and
• Volker Enkelmann

Beilstein J. Org. Chem. 2008, 4, No. 1, doi:10.1186/1860-5397-4-1

• investigation of the Pd-catalyzed dehydrohalogenation is yet not completed, the yield is reproducible higher than with Pd(PPh3)2Cl2, as we reported before [29]. 11 was demethylated with BBr3, the resulting free phenol 12 iodinated with iodine and sodium iodide, and diiodide 13 realkylated with dimethylsulfate

Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes

• Stephen P. Marsden and
• Pascal C. Ducept

Beilstein J. Org. Chem. 2005, 1, No. 5, doi:10.1186/1860-5397-1-5

• generalisation of the approach has been the paucity of methods for preparing substituted silylketenes.[18][19] Methods based upon the thermolysis of siloxyalkynes [20] and dehydrohalogenation of substituted α-silyl acid halides [21][22] have not found general application. We recently reported a mild and