1,3-Dipolar Cycloadditions of Diazomethane to Chiral Electron-Deficient Olefins:  The Origin of the π-Facial Diastereoselection

Abstract

The stereochemical outcome of diazomethane cycloadditions to several chiral electron-deficient olefins has been investigated in order to establish the origin of the pi-facial diastereoselection. Nitro olefins, vinyl sulfones, enoates, and 2-amino enoates have been used for such a purpose. These substrates have been prepared from D-glyceraldehyde acetonide through Wittig-type condensations and present an alkoxy substituent, provided by the bulky dioxolane ring, attached to the stereogenic allylic carbon. Syn-adducts have been obtained in all cases as the major isomers, independently of the Z/E stereochemistry of the double bond and the number and the nature of the substituents, the chirality of the asymmetric allylic carbon being the only thing responsible for the diastereoselection. Theoretical calculations show that steric hindrance due to the bulky dioxolane group is the main factor governing the preference for the syn-attack of diazomethane to the olefinic double bond.

Highly stereoselective and easy synthesis of enantiopure phosphoranyl oxiranes

“…This result is in accordance with the stereochemical outcome of the addition of diazomethane 19 and diazo compound 1 15 to chiral olefins derived from aldehyde 4, which were previously investigated in our laboratory.…”

Pitfalls in the chemistry of cellulosic key chromophores

“…It was the heterocycle 5,8-dihydroxy-1H-benzo[f]indazole -4,9dion (29), which had evidently been formed by a [1,3]-dipolar cycloaddition ([3 ? 2]-cycloaddition of diazomethane (Houk and Luskus 1970;Muray et al 2000)) to the quinoid C2-C3-double bond in DHNQ, followed by oxidation of the primary intermediate 28.…”

Synthesis of Cyclic Hydrazino α-Carboxylic Acids

“…Studies of diastereoselective 1,3-dipolar cycloadditions with alkenes 71-75 and related derivatives of chiral allyl alcohols are a good example for this variability with respect to the stereochemical outcome of these reactions. 70 Substrates 71-75 ( Figure 6) have been used extensively for 1,3-dipolar cycloadditions with diazoalkanes to give syn-and anti-pyrazolines 76-80 (dependent upon alkene geometry) with high diastereoselectivity (Table 7). It is interesting to note that anti-configured cycloaddition products predominate if chiral allyl amines are used as educts.…”