Single and double stereoselective fluorination of (E)-allylsilanes

• Marcin Sawicki,
• Angela Kwok,
• Matthew Tredwell and
• Véronique Gouverneur

Beilstein J. Org. Chem. 2007, 3, No. 34, doi:10.1186/1860-5397-3-34

• these substrates suffered from a poor level of diastereocontrol, thereby limiting the synthetic value of these reactions.[16][17] The absence of a silylated stereogenic centre is likely to be responsible for the poor stereocontrol observed upon fluorination of these substrates. We envisaged that the

• crude mixture and its structure was tentatively assigned as syn (Z)-2e (entry 1). The benzyl-substituted allylsilane anti-1f was fluorinated in 90% yield with a similar sense and level of stereocontrol (entry 2). Excellent transfer of chirality was also observed for the fluorination of anti (E)-1g

• demanding and required higher temperature to reach completion. Under these conditions, the level of stereocontrol of the second fluorination was moderate (Scheme 3). To unambiguously confirm the stereochemistry of syn (E)-3 [major diastereomer], this compound was converted into the known symmetrical

Allylsilanes in the synthesis of three to seven membered rings: the silylcuprate strategy

• Asunción Barbero,
• Francisco J. Pulido and
• M. Carmen Sañudo

Beilstein J. Org. Chem. 2007, 3, No. 16, doi:10.1186/1860-5397-3-16

• under Lewis acid catalysis. [10] Thus, silicon assisted cyclization of oxoallylsilanes 3–8 in the presence of TiCl4 or EtAlCl2 results in the formation of 3-methylene-1-cyclopentanols 11–14 with a high degree of stereocontrol (Scheme 3). [7] The cis stereochemistry observed in 11 might indicate a

• -cyclopropane moiety, from open chain allylsilanes in just one step. The high stereocontrol associated to the ring formation allows the synthesis of enantiomerically pure spiro-tricyclic alcohols containing an angular OH-group, such as 38 (Scheme 7). [20] The use of reagents different from organoaluminun

Pd-catalysed [3 + 3] annelations in the stereoselective synthesis of indolizidines

• Olivier Y. Provoost,
• Andrew J. Hazelwood and
• Joseph P. A. Harrity

Beilstein J. Org. Chem. 2007, 3, No. 8, doi:10.1186/1860-5397-3-8

• [3 + 3] annelation of enantiomerically pure aziridine 7 provides the functionalised piperidine 8 that can be elaborated to the indolizidine skeleton in only 4 steps with good stereocontrol. Introduction Indolizidine alkaloids represent one of the most structurally diverse classes of natural products

Contemporary organosilicon chemistry

• Steve Marsden

Beilstein J. Org. Chem. 2007, 3, No. 4, doi:10.1186/1860-5397-3-4

• Chemistry". We have contributions from some of the leading practitioners in the area, covering a wide range of topics including the stereoselective construction of oxygen and nitrogen-containing heterocycles, the use of tethered silicon reagents to deliver acyclic stereocontrol, chiral-at-silicon reagents

Reagent controlled addition of chiral sulfur ylides to chiral aldehydes

• Varinder K. Aggarwal and
• Jie Bi

Beilstein J. Org. Chem. 2005, 1, No. 4, doi:10.1186/1860-5397-1-4

• reversibility in betaine formation, which impacted on the stereocontrol at the C2 position. Introduction The reaction of chiral sulfur ylides with carbonyl compounds, operating in either a catalytic or stoichiometric mode, have emerged as a useful and powerful method in the arsenal of asymmetric

• betaine (high reversibility results in low stereocontrol) whilst the C2 stereochemistry is controlled by the degree of reversibility in syn betaine formation (high reversibility leads to high diastereocontrol in favor of the trans epoxide).[2] We questioned whether the high level of reagent control