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Samarium metal and samarium diiodide have become important tools as selective cyclopropanating agents in organic synthesis due to their high chemo- and stereoselectivity. Therefore, Sm and SmI(2) are the ideal reagents to prepare cyclopropane derivatives. This tutorial review highlights C-C multiple bond cyclopropanation processes promoted by samarium or samarium diiodide.

The synthesis of β-amino esters or amides has been achieved from moderate to high yields from the reaction of imines and α-halo esters or amides promoted by catalytic amounts of samarium diiodide in the presence of magnesium turnings as coreductant. A mechanism is proposed to explain this catalytic samarium( II)-promoted aza-Reformatsky reaction. [ABSTRACT FROM AUTHOR]

A samarium-mediated novel synthesis of enantiopure 4-amino-1,3-diols is carried out through a samarium-promoted aldol-Tishchenko reaction starting from chiral α′-amino-α-chloro ketones (derived from natural α-amino acids) and aldehydes. The process takes place with moderate levels of stereoselectivity and in high yields. A mechanism is proposed to explain these results while the absolute configuration and structure of the aldol-Tishchenko adducts were established by X-ray analysis. This method has also been utilized for the synthesis of enigmols, 1-deoxysphingoid base analogues. [ABSTRACT FROM AUTHOR]

Abstract: A novel reaction of bromonitromethane with a variety of imines in very mild conditions promoted by SmI2 and NaI to afford nitroamines or bromonitroamines is described. When these reactions were performed on sugar-based imines, the corresponding nitroamines or bromonitroamines were obtained in high yields and from moderate to good stereoselectivities. Synthetic possibilities of nitroamines were also shown by their reduction with SmI2/H2O in the presence of pyrrolidine at room temperature. A mechanism is proposed for this novel aza-Henry reaction. [Copyright &y& Elsevier]

An easy, direct, general, and efficient samarium diiodide-mediated preparation of 3-hydroxyacids 1 in high yield by reaction of different aldehydes or ketones with commercially available iodoacetic acid is described. The application of different esterification procedures to the crude 3-hydroxyacids so obtained afforded the corresponding 3-hydroxyesters. Also, the cyclization of crude 3-hydroxycarboxylic acids allowed the preparation of β-lactones. A mechanism is proposed to explain the synthesis of 3-hydroxyacids 1. [ABSTRACT FROM AUTHOR]

Synthesis of (E)-α,β-unsaturated esters in high yields and with total stereoselectivity is achieved from a-halo-b-hydroxy esters promoted by catalytic amounts of SmI2. The starting compounds were easily prepared from a-halo esters and aldehydes as a mixture of stereoisomers. A mechanism is proposed to explain this samarium(II)-promoted catalytic β-elimination reaction. [ABSTRACT FROM AUTHOR]

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 °C. [ABSTRACT FROM AUTHOR]

A novel, efficient, and totally stereoselective synthesis of (E)-α,β-unsaturated primary amides is reported. This process is consistent with a SmI2-mediated sequential reaction of an unmasked tamarium chloroacetamide enolate with an aldehyde, followed by a β-elimination to produce (E)-α,β-unsaturated primary amides in good yields. [ABSTRACT FROM AUTHOR]

An easy, simple, rapid, and nonhazardous deuteration of the C–C triple bond of α,β-acetylenic esters, amides, or acids by means of samarium diiodide in the presence of D2O, provides an efficient method for synthesizing 2,2,3,3-tetradeuterioesters, amides, or carboxylic acids, respectively. When H2O is used instead of D2O, saturated carboxylic esters, amides, or acids were isolated. A mechanism to explain these reduction reactions has been proposed. [Copyright &y& Elsevier]

A samarium-promoted synthesis of (E)-nitroalkenes from 1-bromo-1-nitroalkan-2-ols in high yields and with total selectivity is reported. This reaction together with the easy and efficient preparation of the 1-bromo-1-nitroalkan-2-ols constitutes a simple and advantageous alternative toward nitroalkenes with total E-stereoselectivity. A mechanism is proposed to explain the E-stereoselectivity of the β-elimination reaction. [ABSTRACT FROM AUTHOR]