Radical Cyclization of β-Alkoxymethacrylates: Expedient Synthesis of (+)-Methyl Nonactate

Diastereoselective synthesis of tetrahydrofurans via mead reductive cyclization of keto-beta-lactones derived from the tandem Mukaiyama aldol lactonization (TMAL) process

The development of a diastereoselective, three-step strategy for the construction of substituted tetrahydrofurans from alkenyl aldehydes based on the tandem Mukaiyama aldol-lactonization process and Mead reductive cyclization of keto beta-lactones is reported. Stereochemical outcomes of the TMAL process are consistent with models established for Lewis acid-mediated additions to alpha-benzyloxy and beta-silyloxy aldehydes while reductions of the five-membered oxocarbenium ions are consistent with Woerpel's models. Further rationalization for observed high diastereoselectivity in reductions of alpha-silyloxy 5-membered oxocarbenium ions based on stereoelectronic effects are posited. A diagnostic trend for coupling constants of gamma-benzyloxy beta-lactones was observed that should enable assignment of the relative configuration of these systems.

Enantioselective H-Atom Transfer Reaction: A Strategy to Synthesize Formaldehyde Aldol Products

[reaction: see text] Enantioselective radical alkylation of Baylis-Hillman adducts furnished aldol products in good yield and selectivity. The results illustrate that the selectivity in the hydrogen atom transfer is dependent on the size of the ester substituent, with smaller substituents providing better enantioselectivity.

Intramolecular aminyl and iminyl radical additions to alpha,beta-unsaturated esters. Diastereoselective tandem cyclofunctionalization and hydrogen transfer reactions

[reaction: see text] A tandem process featuring intramolecular aminyl radical cyclofunctionalization and hydrogen transfer affords 2,3-trans-disubstituted pyrrolidines with anti or syn diastereoselectivity. The extension of this strategy to iminyl radicals gives trans-anti pyrrolenines with high levels of 1,2-induction in both steps of the tandem process.

Radical cyclization of beta-aminoacrylates: synthesis of (-)-indolizidine 223AB

[reaction: see text] (-)-Indolizidine 223AB was synthesized via radical cyclization of the beta-aminoacrylate derivative of a trans-2,5-disubstituted pyrrolidine. The trans-2,5-disubstituted pyrrolidine substrate was prepared by radical cyclization of a Ses-protected beta-aminoacrylate.

Radical cyclization of beta-alkoxyacrylates: synthesis of a C2-symmetric, L-shaped molecule with four fused tetrahydropyran rings

A C2-symmetric, L-shaped tetracycle with four fused tetrahydropyran rings was synthesized from (3R, 4R)-1, 6-dibenzoyloxy-hexane-3, 4-diol employing radical cyclization reactions of beta-alkoxyacrylates.