Allyltricarbonyliron lactone complexes

CautionI All procedures should be carried out in a well-ventilated hood, and disposable vinyl or latex gloves and chemical-resistant safety glasses should be worn. 

Clean all glassware, syringes, needles and stirrer bars and dry for at least 2 h in a hot oven ( 100 C) before use. Allow apparatus to cool in a desiccator. 

Assemble a Schlenk tube or round-bottomed flask/nitrogen inlet, place the stirrer bar in the flask or Schlenk and attach a septum to the remaining neck of the vessel. 

Support the flask or Schlenk using a clamp and stand with a heavy base. 

Attach a flexible tubing connection from the vacuum/nitrogen manifold to the gas inlet. 

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Cationic t 3-allyltetracarbonyliron complexes are generated by oxidative addition of allyl iodide to pentacarbonyliron followed by removal of the iodide ligand with AgBF4 under a carbon monoxide atmosphere [35]. Similarly, photolysis of vinyl epoxides or cyclic vinyl sulfites with pentacarbonyliron or nonacarbonyldiiron provides Jt-allyltricarbonyliron lactone complexes. Oxidation with CAN provides by demetallation with concomitant coupling of the iron acyl carbon to one of the termini of the coordinated allyl moiety either [3- or 8-lactones (Scheme 1.12) [36, 37]. In a related procedure, the corresponding Jt-allyltricarbonyliron lactam complexes lead to P- and 8-lactams [37]. 

The TiCLrmediated Mukaiyama aldol reactions between 7r-allyltricarbonyliron lactone complexes and chiral aldehydes were well documented by Ley and coworkers [37]. (/ )-Trimethylsilyl enol ether 23 (>96% ee) was prepared from the methyl ketone complex 22 by treatment with MesSiOTf/EtsN in CH2CI2 and this was then reacted with (R)- and (5)-2-benzyloxypropanal 24 under the influence of TiCl4 in CH2CI2 at -78 °C. Although the reactions proceeded very slowly and apparent hydrolysis of the silyl enol ether occurred, the aldol products 25 and 26 were isolated in excellent diastereoselectivity in both cases (Scheme 1-8). Interest-... 

Ley SV, Burckhardt S (2000) The Use of Tt-Allyltricarbonyliron Lactone Complexes in the Synthesis of the Resorcylic Macrolides a- and p-Zearalenol. J Chem Soc Perkin Trans 1 3028... 

Jt-Allyltricarbonyliron lactone complexe s are useful precursors for organic synthesis. They were first reported in 1964 [254] and have since been shown to be available from a variety of substrates [255]. For example, they may be prepared from alkenyl epoxides or various butenediols [256] and their derivatives by treatment with tetracarbonyl iron [257]. Work in our laboratories had shown that these were useful precursors for a wid5.,range of naturally occurring p and 5-lactones and lactams [258] (Scheme 123). 

While zearalenone has inspired an impressive number of synthetic methodologies (Section 7.3.1), independent syntheses of reduced congeners of this resorcylide are rare. Burckhardt and Ley [91] reported an asymmetric approach to a- and P-zearalenol whereby the it-allyltricarbonyliron lactone complexes (240) are employed... 

Exhaustive carbonylation of Ti-allyltricarbonyliron lactone complexes at elevated temperatures (190 °C) affords S-lactones. The usefulness of this process was demonstrated by a synthesis of the natural product ( )-massoilactone (Scheme 39). Conjugate addition of nickel acylate complexes to enones followed... 

The chemistry of chelated allyl complexes is dominated by ferralactones or 77 -allyltricarbonyliron lactone complexes. These complexes are used extensively in organic synthesis and are obtained by the reaction of an a,/ -unsaturated lactone with Fe(GO)s (Equation (6)). Oxidation of the ferralactone complex with GAN yields the /3-lactone as the major product. ... 

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