The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• Institute of Engineering Science and Technology, Shibpur, PO-Botanic Garden, Howrah-711 103 (WB), India 10.3762/bjoc.15.61 Abstract The LANCA three-component reaction of lithiated alkoxyallenes LA, nitriles N and carboxylic acids CA leads to β-ketoenamides KE in good to excellent yields. The scope of this

• at room temperature in water as solvent and provided the expected acylamido-substituted quinoxalines QU1–7 in moderate to good yields (Table 7) [43][45]. Conclusion Lithiated alkoxyallenes LA, nitriles N and carboxylic acids CA undergo a three-component reaction (LANCA reaction) that affords β

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

• 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

• acyclic and cyclic amino alcohols. Access to enantiopure 3,6-dihydro-1,2-oxazines 3 via lithiated alkoxyallenes 1 and carbohydrate-derived nitrones 2. Iodination of 1,2-oxazines syn-3a–c and anti-3a,d leading to 5-iodo-substituted 1,2-oxazines syn-4a–c and anti-4a,d [TMSE = (2-trimethylsilyl)ethyl

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

• led to undesired side reactions, e.g., deacylation or oligomerization processes. The development of the discussed pyridine syntheses by cyclocondensation reactions of β-ketoenamides was inspired by a serendipitously discovered three-component reaction of lithiated alkoxyallenes, nitriles and

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

• ]-cyclization of D-isoascorbic acid-derived (Z)-nitrone 6 and lithiated TMSE-allene 5. Results and Discussion For our synthesis of new divalent carbohydrate mimetics we required 1,2-oxazine derivatives derived from (Z)-nitrone 6 and lithiated alkoxyallenes. The 4-bromophenyl group should allow transition metal

The Flögel-three-component reaction with dicarboxylic acids – an approach to bis(β-alkoxy-β-ketoenamides) for the synthesis of complex pyridine and pyrimidine derivatives

• Mrinal K. Bera,
• Moisés Domínguez,
• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 394–404, doi:10.3762/bjoc.10.37

• extension of the substrate scope of the Flögel-three-component reaction of lithiated alkoxyallenes, nitriles and carboxylic acids is presented. The use of dicarboxylic acids allowed the preparation of symmetrical bis(β-ketoenamides) from simple starting materials in moderate yields. Cyclocondensations of

• aromatic rings. Flögel-three-component reaction of lithiated alkoxyallenes, nitriles and carboxylic acids providing β-alkoxy-β-ketoenamides 1 – versatile precursors for the synthesis of functionalized N-heteroaromatics 2–6. Synthesis of bis(β-ketoenamides) 13–15 by three-component reactions of lithiated

Stereodivergent synthesis of jaspine B and its isomers using a carbohydrate-derived alkoxyallene as C₃-building block

• Volker M. Schmiedel,
• Stefano Stefani and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2013, 9, 2564–2569, doi:10.3762/bjoc.9.291

• . Keywords: chiral auxiliaries; gold catalysis; jaspine B; lithiated alkoxyallenes; natural product synthesis; pachastrissamine; tetrahydrofurans; Introduction Jaspine B, also known as pachastrissamine (1, Scheme 1), is an anhydrophytosphingosine derivative, isolated 2002 from the marine sponge Pachastrissa

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

• hydroxylated 2H-1,2-oxazine derivatives is presented utilizing the [3 + 3] cyclisation of lithiated alkoxyallenes and an L-erythrose-derived N-glycosyl nitrone as precursors. This key step proceeded only with moderate diastereoselectivity, but allowed entry into both enantiomeric series of the resulting 3,6

• 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

• ][8], these nitrones very often furnish the corresponding products in a highly selective manner. In this context, reactions of lithiated alkoxyallenes with enantiopure nitrones are particularly of interest since they lead by a [3 + 3] cyclisation process to 1,2-oxazine derivatives with excellent

A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction

• Christian Eidamshaus,
• Roopender Kumar,
• Mrinal K. Bera and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

• provide dihydropyridine 6. Elimination of trimethylsilanol and subsequent O-desilylation affords the 4-hydroxypyridine 7 (Scheme 1). The desired β-ketoenamides 4 are either accessible by acylation of enaminoketones or by a multicomponent reaction of lithiated alkoxyallenes, nitriles and carboxylic acids

• enantiopurity [40]. Chiral carboxylic acids are readily available and their use would allow for a rapid access to pyridines with side chains bearing stereogenic centers. In recent years we studied intensively the multicomponent reactions of lithiated alkoxyallenes with nitriles and carboxylic acids and could

Preparation of pyridine-3,4-diols, their crystal packing and their use as precursors for palladium-catalyzed cross-coupling reactions

• Tilman Lechel,
• Irene Brüdgam and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 42, doi:10.3762/bjoc.6.42

• analysed with regard to their photophysical properties. Results and Discussion The preparation of pyridine-3,4-diol derivatives as depicted in Scheme 1 succeeded by using highly substituted trifluoromethyl-substituted 4-hydroxypyridine precursors 1 that have been prepared in two steps from lithiated

• alkoxyallenes, nitriles and carboxylic acids [21]. It is noteworthy, that the respective protecting group at C-3 of the pyridine core was originally incorporated with the alkoxyallene moiety. The mild cleavage of the benzyl-protected pyridine 1a to diol 2a was achieved by hydrogenolysis in the presence of