Total regioselective and diastereospecific iodolysis of 2,3-epoxyamides promoted by SmI2: synthesis of (2R*,3R*)- or (2R,3S)-2-hydroxy-3-iodoamides.

The use of samarium diiodide as a source of iodides is reported. Thus, 2-hydroxy-3-iodoamides were obtained, with total regioselectivity, by treatment of 2,3-epoxyamides, in which the oxirane ring is 2,3-disubstituted or 2,2,3-trisubstituted, with SmI2. The ring-opening reaction was diastereospecific and (2R*,3R*)- or (2R*,3S*)-2-hydroxy-3-iodoamides were obtained from cis- or trans-epoxyamides, respectively. The relative configuration of 2-hydroxy-3-iodoamides was established by X-ray analysis. A mechanism to explain this transformation has been proposed. The starting compounds 1 are easily prepared by the reaction of enolates derived from 2-chloroamides with aldehydes at -78 degrees C.

Synthesis of (E)-alpha-hydroxy-beta,gamma-unsaturated amides with high selectivity from alpha,beta-epoxyamides by using catalytic samarium diiodide or triiodide.

The highly stereoselective synthesis of (E)-alpha-hydroxy-beta,gamma-unsaturated amides starting from alpha,beta-epoxyamides, by using catalytic SmI2 or SmI3, was achieved. This transformation can also be carried out by using SmI2 generated in situ from samarium powder and diiodomethane. The starting compounds 1 are easily prepared by the reaction of enolates derived from alpha-chloroamides with ketones at -78 degrees C. A mechanism to explain this transformation has been proposed. Cyclopropanation of (E)-alpha-hydroxy-beta,gamma-unsaturated amides has been performed to demonstrate their synthetic applications.

The first transformation of aliphatic alpha,beta-epoxyamides into alpha-hydroxyamides.

A general synthesis of aliphatic alpha-hydroxyamides with total regioselectivity by a reductive cleaveage of the C(beta)-O bond of aliphatic alpha,beta-epoxyamides, promoted by samarium diiodide and MeOH, is described. The treatment of enantiopure aliphatic alpha,beta-epoxyamides afforded enantiomerically enriched aliphatic alpha-hydroxyamides. A radical mechanism has been proposed to explain this reaction. [reaction: see text]

Synthesis of aromatic (E)- or (Z)-alpha,beta-unsaturated amides with total or very high selectivity from alpha,beta-epoxyamides and samarium diiodide.

Highly stereoselective synthesis of aromatic alpha,beta-unsaturated amides was achieved by treatment of aromatic alpha,beta-epoxyamides with samarium diiodide. The starting compounds 1 and 3 are easily prepared by the reaction of enolates derived from alpha-chloroamides with carbonyl compounds at -78 degrees C. A mechanism to explain this transformation is proposed.

Transformation of alpha,beta-epoxyesters into 2,3-dideuterioesters promoted by samarium diiodide.

An easy and general sequenced elimination/reduction process by means of samarium diiodide, in the presence of D(2)O, provides an efficient method for synthesizing 2,3-dideuterioesters 2. The reaction can be also carried out in the presence of H(2)O instead of D(2)O, yielding the corresponding saturated esters 4. Other deuterated esters have been also obtained. A mechanism to explain this synthesis has been proposed.

Synthesis of (E)-alpha,beta-unsaturated esters with total or high diastereoselectivity from alpha,beta-epoxyesters.

[reaction: see text] High stereoselective beta-elimination in 2,3-epoxyesters 1 was achieved using samarium diiodide, yielding alpha,beta-unsaturated esters 2, in which the C=C bond is di-, tri- or tetrasubstituted. The starting compounds 1 are easily prepared by reaction of the corresponding lithium enolates of alpha-chloroesters with aldehydes or ketones at -78 degrees C. The influence of the reaction conditions and the structure of the starting compounds in the stereoselectivity of the beta-elimination reaction is also discussed.