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

• appropriate amine (PMBNH2 or BnNH2 respectively) with ethyl E-4-chloro-3-methoxybut-2-enoate.[11] Reaction of 4b with n-BuLi as before followed by TMSCl to generate 5b, and reaction with aldehyde 7 (0.7 equiv) as limiting reagent using SnCl4 (2 equiv) as the Lewis-acid promoter with rapid stirring of the

• would have presented steric hindrance at nitrogen towards the Lewis-acid. We have also previously reported on the use of 4-methoxy-2-trimethylsilyloxypyrroles for generating C-5 quaternary centres using trimethyl orthoformate as the electrophile and BF3·OEt2 as the promoter.[10] Together with the

The first organocatalytic carbonyl- ene reaction: isomerisation- free C-C bond formations catalysed by H-bonding thio- ureas

• Matthew L. Clarke,
• Charlotte E. S. Jones and
• Marcia B. France

Beilstein J. Org. Chem. 2007, 3, No. 24, doi:10.1186/1860-5397-3-24

• was carried out (Scheme 2 and Table 1). N,N'-di [3,5-bis(trifluoromethyl)phenyl]thiourea 5,[18], emerged as by far the most active promoter for this reaction. The catalyst was used at 20 mol % loading and compared against a control reaction with no catalyst. Products were isolated by chromatography

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• (Scheme 3).[10][11] Finally, in a recent report, Porter has described the intramolecular Pauson-Khand reaction of allyldimethyl- and allyldiphenylsilyl propargyl ethers promoted by dicobalt octacarbonyl and n-butyl methyl sulphide as a promoter to give the bicycles in modest to good yields (Scheme 4).[12

• each compound were first prepared and characterised, prior to addition of the promoter. Unfortunately, none of the promoters gave any of the desired products but simply de-complexed starting materials were recovered in each case. Alternative metal carbonyls were also investigated, with compounds 1–4

Asymmetric aza-Diels- Alder reaction of Danishefsky's diene with imines in a chiral reaction medium

• Bruce Pégot,
• Olivier Nguyen Van Buu,
• Didier Gori and
• Giang Vo-Thanh

Beilstein J. Org. Chem. 2006, 2, No. 18, doi:10.1186/1860-5397-2-18

• )-(-)-methylbenzylamine chiral auxiliary. However, all reactions had to be performed in an organic solvent under an inert atmosphere and required stoichiometric loadings of Lewis acid promoter, the use of which is not recommended under 'green chemistry' conditions. Having established the high efficiency of chiral ILs is

Colchitaxel, a coupled compound made from microtubule inhibitors colchicine and paclitaxel

• Karunananda Bombuwala,
• Thomas Kinstle,
• Vladimir Popik,
• Sonal O. Uppal,
• James B. Olesen,
• Jose Viña and
• Carol A. Heckman

Beilstein J. Org. Chem. 2006, 2, No. 13, doi:10.1186/1860-5397-2-13

• transiently by promoter treatment [58]. The phenotype induced by the microtubule inhibitor combination is qualitatively similar to that of promoter-treated cells but differs in direction. Therefore, reversal of cancer cell phenotype suggested that the same downstream mechanisms, i.e. the activation or