57278-89-4Relevant academic research and scientific papers
Fate of the intermediate diradicals in the caldera: Stereochemistry of thermal stereomutations, (2 + 2) cycloreversions, and (2 + 4) ring-enlargements of cis- and trans-1-cyano-2-(E and Z)-propenyl-cis-3,4-dideuteriocyclobutanes
Doering, W. von E.,Cheng, Xueheng,Lee, Kyuwang,Lin, Zisen
, p. 11642 - 11652 (2002)
This paper addresses the decades-old problem of gaining a measure of intellectual control over the fate of the diradical intermediate in not-obviously-concerted thermal rearrangements. It focuses mainly on the stereochemistry of the thermal rearrangement of cis- and trans-1-cyano-2-trans-propenylcyclobutane to the related ring-enlarged products, 4-cyano-3-methylcyclohexenes. The complete stereochemical profile is revealed by the incorporation of a pair of cis deuterons to serve as a stereochemical lighthouse. The striking result (besides providing a further example of the inapplicability of the orbital symmetry rules of Woodward and Hoffmann to not-obviously-concerted reactions) is the predominance of the same stereoisomer regardless whether starting from the cis or trans educt. This preference is rationalized by a simple conceptual scheme based on two premises of the behavior of the diradical as intermediate: removal of the diradical from the caldera of rotationally labile conformations occurs whenever the two radical centers come within bonding distance in an appropriate orientation of orbitals; relative internal rotational rates are in the order, cyanomethyl faster than methallyl, faster than internal rotation about the backbone.
Endo-selective Diels-Alder reaction of methacrylonitrile: application to the synthesis of Georgywood
Borosy, Andras,Frater, Georg,Müller, Urs,Schr?der, Fridtjof
experimental part, p. 10495 - 10505 (2010/02/28)
Diels-Alder reactions of alkyl-substituted dienes with acrylonitriles give good yields and endo-selectivities if catalyzed by (organo)aluminum, (organo)boron or gallium halides. The activity of these group IIIa Lewis acids in this reaction correlates with
