Asymmetric Simmons–Smith Reaction of Allylic Alcohols with Al Lewis Acid/N Lewis Base Bifunctional Al(Salalen) Catalyst

Abstract

Schonend zum Dreiring: Hoch enantioselektive Simmons‐Smith‐Reaktionen mit trans‐disubstituierten Allylalkoholen gelingen bei Raumtemperatur in Gegenwart katalytischer Mengen eines Aluminium‐Salalen‐Komplexes (siehe Schema).

Highly Efficient Asymmetric Simmons–Smith Cyclopropanation Promoted by Chiral Heteroorganic Aziridinyl Ligands

“…Ligand 1 a bearing an achiral aziridine a was used to check the effect of the stereogenic center located at the sulfinyl moiety on the stereochemical course of the reaction. By following the method described previously,2 we have chosen cyclopropanation of cinnamyl alcohol ( 2 ) for the screening of our ligands. The reactions were performed for 5 h (after optimization) in dichloromethane with 2 equiv.…”

“…On the basis of the best results obtained with ligand 1 b , we decided to check the scope of the reaction of several allylic alcohols2 in the presence of ligand 1 b as the catalyst under the same conditions as used previously (Scheme ). The results are summarized in Table 2.…”

“… [a] In chloroform ( c 1) at room temperature; [b] Determined from chiral HPLC analysis; [c] According to literature data 2…”

“…Enantiomerically pure substituted cyclopropanes attract a great deal of attention from chemists because they constitute a basic structural element in a wide range of natural products. One of the most frequently used methods of their synthesis is the asymmetric Simmons–Smith cyclopropanation of various alkenes, particularly of allylic alcohols 2. In this case, the stereoselective Simmons–Smith reaction catalyzed with chiral ligands serves as an effective method for the preparation of cyclopropylmethanol derivatives, which are useful building blocks for organic synthesis 3–6.…”

Highly Enantioselective Synthesis of 1,2,3‐Substituted Cyclopropanes by Using α‐Iodo‐ and α‐Chloromethylzinc Carbenoids

“…[7] Subsequently, numerous substituted carbenoids were developed by using this strategy with other gem-diiodomethyl motifs (RCHI 2 ) and were employed for the formation of the corresponding cyclopropanes. [8] Along with these advances, several enantioselective cyclopropanation reactions of allylic alcohols were developed by using both unsubstituted [9,10] and substituted [11] iodoalkylzinc reagents. The high levels of enantio-and diastereoselectivity observed in the preparation of 1,2,3-substitued cyclopropanes by using alkyl-substituted zinc carbenoids and allylic alcohols in the presence of a dioxaborolane-derived chiral ligand clearly illustrate the potential of substituted zinc carbenoids in synthesis.…”