777918-01-1Relevant academic research and scientific papers
Fate of diradicals in the caldera: Stereochemistry of thermal stereomutation and ring enlargement in cis- and trans-1-cyano-2(E)- propenylcyclopropanes
Doering, William Von E.,Barsa, Edward Albert
, p. 12353 - 12362 (2007/10/03)
This study of thermally induced stereomutation and ring enlargement in both (-)-trans-1-cyano-2(E)-propenylcyclopropane [(-)-trans-1] and (+)-cis-1-cyano-2(E)-propenylcyclopropane [(+)-cis-1] to cyclopentenes definitively contraindicates the usefulness of Woodward-Hoffmann rules of orbital symmetry as a theoretical basis for predicting the stereochemistry of the products. From both diastereomers, the same (+)-trans-4-cyano-3- methylcyclopentene [(+)-trans-2] is the major product among the four diastereomeric products, "allowed" and formally the result of a single internal rotation of the cyano-bearing carbon atom from (-)-trans-1, "forbidden" and the result of zero internal rotations from (+)-cis-1. Stereomutation and ring enlargement are discussed in detail in terms of rotational propensity, thermodynamic preference, and the possible role of diradicals in transit and diradicals as intermediates in a caldera.
Site and stereoselectivity of the cyclopropanation of unsymmetrically substituted 1,3-dienes by the Simmons-Smith reaction
Guerreiro, Mario Cesar,Schuchardt, Ulf
, p. 1793 - 1800 (2007/10/03)
In the Simmons-Smith reaction, 1,3-dienes are preferentially cyclopropanated at the more electron-rich double bond to afford the trans-vinylcyclopropane; an allylic hydroxyl group increases the reactivity and directs the cyclopropanation to the adjacent double bond.
