One-pot nucleophilic substitution–double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

• Hans-Ulrich Reissig and
• Fei Yu

Beilstein J. Org. Chem. 2023, 19, 1399–1407, doi:10.3762/bjoc.19.101

• carbohydrate mimetics, but the reductive cleavage of the 1,2-oxazine rings to aminopyran moieties did not proceed cleanly with these compounds. Keywords: alkynes; azides; copper catalysis; nucleophilic substitution; 1,2-oxazines; Introduction The concept of click reactions [1][2], in particular, the

Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

• Hisato Shimizu,
• Akira Yoshimura,
• Keiichi Noguchi,
• Victor N. Nemykin,
• Viktor V. Zhdankin and
• Akio Saito

Beilstein J. Org. Chem. 2018, 14, 531–536, doi:10.3762/bjoc.14.39

• ) reaction of N-acylnitroso species with dienes provides the facile and highly stereoselective synthesis of 1,2-oxazines, which have been widely recognized as useful synthons in the synthesis of biologically active natural products [1]. Generally, in the presence of dienes, acylnitroso species are in situ

Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

• Michal Medvecký,
• Igor Linder,
• Luise Schefzig,
• Hans-Ulrich Reissig and
• Reinhold Zimmer

Beilstein J. Org. Chem. 2016, 12, 2898–2905, doi:10.3762/bjoc.12.289

• Michal Medvecky Igor Linder Luise Schefzig Hans-Ulrich Reissig Reinhold Zimmer Freie Universität Berlin, Institut für Chemie und Biochemie, Takustrasse 3, D-14195 Berlin, Germany 10.3762/bjoc.12.289 Abstract Iodination of carbohydrate-derived 3,6-dihydro-2H-1,2-oxazines of type 3 using iodine and

• . This was exemplarily demonstrated by the hydrogenation of syn-21 and anti-24 and by a click reaction of a 5-alkynyl-substituted precursor. Keywords: amino alcohol; click reaction; cross-coupling reactions; hydrogenation; iodination; 1,2-oxazines; Introduction Over the last decade, we have intensively

• studied syntheses and applications of 3,6-dihydro-2H-1,2-oxazines of type 3 [1][2]. These N,O-heterocycles are easily prepared in enantiopure form by a stereodivergent [3 + 3] cyclization of carbohydrate-derived nitrones 2 and lithiated alkoxyallenes 1 (Scheme 1) [3][4]. Subsequently we investigated

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• biologically active compounds. It is a variant of the Diels–Alder reaction where either the diene or the dienophile contains a heteroatom. Hetero-Diels–Alder reactions between conjugated dienes and nitroso dienophiles affording 1,2-oxazines are utilized for the synthesis of many biologically active molecules

• regioselectivity were shown to be valid for a number of simple hetero-Diels–Alder products 72–79 (Figure 4). The hetero-Diels–Alder reaction in the solid phase has been studied to a far lesser degree. However, an analysis of the available data for a number of 1,2-oxazines 80–84 indicates, that, in most cases, the

• regioselectivity of carbamoylbenzyl 1,2-oxazines prepared from diene 89 and benzyl nitrosoformate (96) in solution (derivative 97) [100] and 4-substituted benzyl nitrosoformates on a solid support (derivatives 91–95) [78]. It is obvious that although the substitution on benzyl nitrosoformate is quite distant from

Synthesis of rigid p-terphenyl-linked carbohydrate mimetics

• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 1749–1758, doi:10.3762/bjoc.10.182

• mimetics; hydrogenolysis; multivalent glycosystems; 1,2-oxazines; samarium diiodide; Suzuki cross-coupling; Introduction Carbohydrates are the class of biomolecules with the highest structural diversity [1][2]. Specific carbohydrates are responsible for cell-type specific interactions [3] and they are

• observed. Due to the complexation of lithiated allene 9 to the nitrone 6 an exclusive formation of the two syn-1,2-oxazines 4 was observed. This result suggests that the configuration at C-2 of the dioxolane moiety has no influence on the stereochemical outcome of the reaction. The model suggested by

• -substituted 1,2-oxazines to bicyclic ketones has been described in many examples [24]. Gratifyingly, starting from 1,2-oxazine 4 with tin(IV) chloride as Lewis acidic promoter the corresponding ketone was obtained in excellent stereoselectivity. The subsequent protection of the primary hydroxy group as TBS

Synthesis of new enantiopure poly(hydroxy)aminooxepanes as building blocks for multivalent carbohydrate mimetics

• Léa Bouché,
• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 213–223, doi:10.3762/bjoc.10.17

• ; 1,2-oxazines; rearrangements; reductions; Introduction Since carbohydrates play a crucial role in biochemistry, compounds mimicking their structure and/or function (carbohydrate mimetics) have attracted great attention in academic research and in drug development [1][2][3]. These mimetics should not

• ]. The general approach is shown in Scheme 1: the chiral pool-derived nitrones A [29][30] undergo a [3 + 3]-cyclization with lithiated [2-(trimethylsilyl)ethoxy]allene (TMSE-allene) [31] as C-3 building block [32] to form the 3,6-dihydro-2H-1,2-oxazines B; subsequent Lewis acid-promoted reactions [23

• a Dondoni protocol [29]. This route allows the synthesis of enantiopure nitrone 3 in multi-gram scale. The enantiopure (Z)-configured nitrones 6, 8 and 3 were treated with in situ lithiated TMSE-allene at −78 °C furnishing the expected 1,2-oxazines syn-7 [37], syn-9 and syn-10 in high yields and

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• -dihydro-2H-1,2-oxazines. Their enol ether double bond was then subjected to a hydroboration followed by an oxidative work-up, and finally the auxiliary was removed. The described three-step procedure enabled the synthesis of enantiopure hydroxylated 1,2-oxazines. Typical examples were treated with

• samarium diiodide leading to enantiopure acyclic aminopolyols. We also report on our attempts to convert these compounds into enantiopure hydroxylated pyrrolidine derivatives. Keywords: aminopolyols; carbohydrates; chiral auxiliaries; lithiated alkoxyallenes; 1,2-oxazines; pyrroles; pyrrolidines; samarium

• diastereoselectivity [9]. We previously reported on the unusually diverse synthetic potential of carbohydrate-derived 1,2-oxazines allowing the smooth and flexible preparation of various highly functionalised compounds, including de novo syntheses of carbohydrates and their mimetics, as well as N-heterocycles [10][11

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• efficient preparation include Prins cyclizations, intramolecular substitutions, ring closure metathesis, and hetero Diels–Alder reactions [1][2]. Our group recently reported the synthesis of enantiopure aminopyrans employing as the key step a Lewis acid induced rearrangement of 1,2-oxazines to bicyclic

• acids can reverse the stereochemical outcome of these reactions [10] allowing, for example, a stereodivergent access to enantiopure 1,2-oxazines [11]. When lithiated enol ethers 1 were used as the organometallic species in the addition to nitrones 2 [12][13][14], either syn- or anti-configured

Palladium- catalyzed cross coupling reactions of 4-bromo- 6H-1,2-oxazines

• Reinhold Zimmer,
• Elmar Schmidt,
• Michal Andrä,
• Marcel-Antoine Duhs,
• Igor Linder and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2009, 5, No. 44, doi:10.3762/bjoc.5.44

• .5.44 Abstract A number of 4-aryl- and 4-alkynyl-substituted 6H-1,2-oxazines 8 and 9 have been prepared in good yields via cross coupling reactions of halogenated precursors 2, which in turn are easily accessible by bromination of 6H-1,2-oxazines 1. Lewis-acid promoted reaction of 1,2-oxazine 9c with 1

• -hexyne provided alkynyl-substituted pyridine derivative 12 thus demonstrating the potential of this approach for the synthesis of pyridines. Keywords: alkyne; halogenation; 1,2-oxazines; palladium catalysis; pyridines; Introduction A broad range of synthetic applications demonstrates that 1,2-oxazine

• derivatives constitute a versatile class of N,O heterocycles [1][2][3][4][5][6][7][8][9][10][11][12][13]. Considerable attention has been paid to 6H-1,2-oxazines 1 bearing a C-4,C-5-double bond [14][15][16][17][18], which are useful intermediates in the synthesis of γ-lactams [19], γ-amino acids [20], amino