Complete transfer of chirality in an intramolecular, thermal [2 + 2] cycloaddition of allene-ynes to form non-racemic spirooxindoles

• Kay M. Brummond and
• Joshua M. Osbourn

Beilstein J. Org. Chem. 2011, 7, 601–605, doi:10.3762/bjoc.7.70

• spirooxindoles for application to natural product synthesis [5][6][7]. Herein, we disclose preliminary results demonstrating a complete transfer of chiral information from a chiral non-racemic allene-yne to form an enantiomerically enriched spirooxindole in a [2 + 2] cycloaddition reaction. Findings This study

An efficient and practical entry to 2-amido-dienes and 3-amido-trienes from allenamides through stereoselective 1,3-hydrogen shifts

• Ryuji Hayashi,
• John B. Feltenberger,
• Andrew G. Lohse,
• Mary C. Walton and
• Richard P. Hsung

Beilstein J. Org. Chem. 2011, 7, 410–420, doi:10.3762/bjoc.7.53

• (for reviews on pericyclic ring-closures see [83][84], for reviews on ring-closure in natural product synthesis see [85][86], for recent examples of 6π-electron electrocyclic ring-closure see [87][88][89][90][91][92][93], for examples on accelerated ring-closures of 1,3,5-hexatrienes see [94][95][96

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• acetylene in the presence of ruthenium carbene complexes has been reported [11]. A challenge that has still to be faced is the EYCM starting from acyclic internal olefins. Selected ruthenium catalysts able to perform EYCM. Applications of EYCM with ethylene in natural product synthesis. Interaction of

Recent advances in the development of alkyne metathesis catalysts

• Xian Wu and
• Matthias Tamm

Beilstein J. Org. Chem. 2011, 7, 82–93, doi:10.3762/bjoc.7.12

• natural product synthesis and advanced material science [1]. Alkyne metathesis, which deals with the breaking and making of C–C triple bonds, has only relatively recently become part of the tool box of organic and polymer chemists for the preparation of their target molecules [2][3][4][5][6][7][8][9][10

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• and natural product synthesis, a broad application of catalytic C–N-arylation is highly desirable. Evano et al. recently reviewed copper-mediated C–N-arylation reactions in natural product syntheses and discussed different examples from total synthesis using the arylation of alkylamines, amides

• different biological functions including anti-tumour activity and are used as insulin mimetics. The palladium-catalysed coupling of styrene 20 with sterically demanding N-nucleophiles 21 gave the indole building blocks 22 for the natural product synthesis (Scheme 6). In this case, P(t-Bu)3 was the

The allylic chalcogen effect in olefin metathesis

• Yuya A. Lin and
• Benjamin G. Davis

Beilstein J. Org. Chem. 2010, 6, 1219–1228, doi:10.3762/bjoc.6.140

• factors, such as the nature of the catalyst, steric crowding around the alkene and the directing effects of nearby heteroatoms. These factors are of great importance, especially when optimizing reaction conditions for delicate natural product synthesis or protein modification. Interestingly, the

Synthesis of some novel annulated pyrido[2,3-d]pyrimidines via stereoselective intramolecular hetero Diels–Alder reactions of 1-oxa-1,3-butadienes

• Mohit L. Deb and
• Pulak J. Bhuyan

Beilstein J. Org. Chem. 2010, 6, No. 11, doi:10.3762/bjoc.6.11

• preparation of these complex molecules. However, there still remains many challenges in the synthesis of these naturally occurring complex molecules [22][23][24][25][26][27][28][29][30][31]. Hetero Diels–Alder reactions [32][33][34][35] are becoming a mainstay of heterocyclic and natural product synthesis

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• would allow the use of the Friedel–Crafts reactions in the late stages of complex natural product synthesis or in the preparation of biological relevant molecules, including pharmaceuticals and agrochemicals. Furthermore, the extension of substrate scope away from π-activated alcohols and double bonds

Reduction of arenediazonium salts by tetrakis(dimethylamino)ethylene (TDAE): Efficient formation of products derived from aryl radicals

• Mohan Mahesh,
• John A. Murphy,
• Franck LeStrat and
• Hans Peter Wessel

Beilstein J. Org. Chem. 2009, 5, No. 1, doi:10.3762/bjoc.5.1

• convenient. Further extensions of this methodology in the construction of several heterocyclic ring systems and complex synthetic targets for natural product synthesis are currently in progress in our laboratory. Aza- and thia-substituted electron donors. Radical-polar crossover reaction of arenediazonium

Vinylogous Mukaiyama aldol reactions with 4-oxy-2-trimethylsilyloxypyrroles: relevance to castanospermine synthesis

• Roger Hunter,
• Sophie C. M. Rees-Jones and
• Hong Su

Beilstein J. Org. Chem. 2007, 3, No. 38, doi:10.1186/1860-5397-3-38

• 16. Structure of 6a with numbering to demonstrate numbering system used in this section. An example of a vinylogous Mukaiyama aldol in a natural product synthesis. Reagents and conditions: a) RCHO 2, SnCl4 (1.2 equiv), ether, -85°C. Our vinylogous Mukaiyama aldol reaction with different substituents

Synthesis of 2,6-trans- disubstituted 5,6-dihydropyrans from (Z)-1,5-syn-endiols

• Eric M. Flamme and
• William R. Roush

Beilstein J. Org. Chem. 2005, 1, No. 7, doi:10.1186/1860-5397-1-7

• enantioselectivity.[1] In connection with an ongoing natural product synthesis project, we were interested in developing methods to transform diols 2 into dihydropyrans 3 or the enantiomeric dihydropyrans ent-3 through complementary, regioselective cyclodehydration processes (Scheme 1). 2,6-Disubstituted