Jose M. Concellon

β-Elimination reactions by using samarium diiodide

The development of methodologies for the formation of carbon–carbon double bonds could be considered one of the most important challenges in organic synthesis. To this end, β-elimination reactions in 1,2-difunctionalised substrates have been one of the most important means of generating CC bonds. This review is intended to highlight the use of SmI2 in β-elimination procedures, such that the organization of this revision highlights conventional β-elimination processes which are promoted by samarium diiodide. The synthetic applications of SmI2 will be covered, and 1,2-elimination reactions which are involved in sequential reactions promoted by samarium diiodide, will also be illustrated. These methodologies along with the more recent developments in the area are discussed in this tutorial review.

Samarium-Mediated beta-Elimination in Dihalo Alcohols: Diastereoselective Synthesis of (Z)-Vinyl Halides.

High diastereoselectivity in beta-elimination reactions of O-acetyl 1,1-dihaloalkan-2-ols to give (Z)-vinyl halides was achieved by using samarium diiodide [Eq. (1)]. The reaction was also highly diastereoselective and totally chemoselective when a mixture of diastereoisomers was used as substrate (X(1), X(2)=halogen; X(1) not equal X(2)).

The first direct preparation of chiral functionalised ketones and their synthetic uses

Almost enantiomerically pure halogenated α-hydroxy and α-amino ketones can be prepared from O-protected lactates and tribenzylated alanine, respectively; whilst amino ketones 3g have also been transformed into the amino epoxide 7 with high diastereoselectivity.

Sequential Elimination–Reduction Reactions Promoted by Samarium Diiodide: Synthesis of 2,3‐Dideuterioesters or ‐amides

A facile and general sequential elimination/reduction process promoted by samarium diiodide provides an efficient method for synthesizing saturated esters or amides 3 from readily available starting materials. The reaction involves a beta-elimination of the starting 2-halo-3-hydroxyesters or -amides 1 and subsequent 1,4-reduction of the obtained alpha,beta-unsaturated esters or amides in the presence of H2O. When D20 is used instead of H2O, 2,3-dideuterioesters or -amides 4 are isolated. A mechanism is proposed to account for this synthesis.

Addition Reactions of Chloro- or Iodomethyllithium to Imines. Synthesis of Enantiopure Aziridines and β-Chloroamines

We report a novel, simple, and efficient synthesis of aziridines and 1-chloroalkan-2-amines by the reaction of imines derived from various aldehydes and p-toluenesulfonamide or benzenesulfonamide with iodo- or chloromethyllithium, respectively. Both halogenated anions were generated in situ by treatment of diiodo- or chloroiodomethane with methyllithium at -78 or 0 degrees C. The reaction of in situ generated iodo- or chloromethyllithium could also be performed from chiral 2-aminoaldimines to yield enantiopure aziridines or (2S,3S)-2,3-diamino-1-chloroalkanes with high stereoselectivity.

An improved preparation of epoxides from carbonyl compounds by using diiodomethane/methyllithium: synthetic applications

Abstract Synthesis of epoxides starting from different carbonyl compounds is easily carried out by using a diiodomethane and methyllithium at 0°C and a short reaction time. Starting from α-aminoaldehydes the reaction affords amino epoxides, with high diastereoselectivity. The products were transformed into 1,3-diaminoalkan-2-ols by treatment with different amines.

Synthesis of Isotopically Labeled (E)‐β,γ‐Unsaturated Esters with Total or High Diastereoselectivity by Using Samarium Diiodide

A simple, efficient, highly diastereoselective method for preparing (E)-α,δ-dideuterio-β,γ-unsaturated esters: SmI2 -promoted reduction/elimination of α-halo-β-hydroxy-γ,δ-unsaturated esters in the presence of D2 O. This provides the desired products in which the C-C double bond is generated with total or high diastereoselectivity.

Synthesis of Different Deuterated Carboxylic Acids from Unsaturated Acids Promoted by Samarium Diiodide and D2O

An easy, and rapid reduction of the Cdbond;C bond of alpha,beta-unsaturated acids by means of samarium diiodide in the presence of D(2)O provides an efficient method for synthesizing 2,3-dideuterio acids. Starting from alka-2,4-dienoic acids, (E)-alpha,delta-dideuterio-betagamma-unsaturated acids are obtained, the new Cdbond;C bond being generated with complete diastereoselectivity. When H(2)O is used instead of D(2)O, saturated carboxylic acids and (E)-beta,gamma-unsaturated acids are isolated. A mechanism to explain each synthesis has been proposed.

Synthesis of (E)-α,β-Unsaturated Amides with High Selectivity by Using Samarium Diiodide

Stereoselective β-elimination of 2-chloro-3-hydroxyamides 1 is achieved by using samarium diiodide to yield α,β-unsaturated amides 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 α-chloroamides with aldehydes or ketones at −78 °C. The influence of the reaction conditions and the structure of the starting compounds on the stereoselectivity of the β-elimination reaction is also discussed.

Nucleophilic ring closure and opening of aminoiodohydrins

Abstract Enantiopure aminoiodohydrins obtained from α-aminoaldehydes and Sm/CH 2 I 2 have been transformed into regioisomeric aminoiodohydrins, aminoepoxides, azetidines or 1,3-oxazolidines. The key step in these transformations is a nucleophilic opening–closing process.