Butyrolactones, syntheses

Burstein C, Tschan S, Xie X, Glorius F (2006) N-Heterocyclic carbene-cata-lyzed conjugate umpolung for the synthesis of y-butyrolactones. Synthesis 2006 2418-2439... 

Reaction of ketyls. The carbonyl group reacts with Smlj to generate ketyl species which may be reduced further. Capture of the ketyls with suitable reactants expands the utility of the samarium chemistry. Important reactions include butyrolactone synthesis that is amenable to asymmetric induction when chiral acrylic esters are employed. The reagent system (catalytic in Smij) generated in situ from Smij and Zn-Hg is more economical. The system also contains Lil and MCjSiOTf, and in practice MejSiOTf is added to the mixture of the other components at just the rate to maintain a light blue color (indicating the presence of Smij). When Nilj is added as a catalyst, p-propiolactone instead of acrylic esters can be used. Sometimes steric factors preclude cyclization, and 7-hydroxy esters result. Ketyl addition to acrylamides opens a route to 1,4-amino alcohols. ... 

Scheme 70. Chiral y-butyrolactone synthesis mediated by Sml2...

One of the obvious alternatives to butyrolactone synthesis from ester enolates and epoxides is to use nucleophilic attack by ester homo-enolates (vide supra) onto aldehydes and ketones. Two further versions of this latter method are condensations between ketones and methyl 3-bromopropionate using a lanthanum metal to provide the... 

Greene, A. E., J.-C. Muller, and G. Ourisson A New Approach to a-Methylene-y-butyrolactones. Synthesis of (—)-Frullanolide. Tetrahedron Letters 1972, 2489. 

Uneyama, K. Nanbu, H. Torii, S. (1986b) An SnCb-promoted a-methylene-y-butyrolactone synthesis in an aqueous medium, Chem. Lett., 1201-2. 

Lactones General Synthesis Synthesis of P-Lactones Synthesis of Butyrolactones Synthesis of Butenolides Synthesis of Phthalides Synthesis of Tetronic Acids Synthesis of a-Methylenebutyrolactones Synthesis of Valerolactones... 

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