Catalytic Asymmetric Ring Opening of 2,3-Substituted Norbornenes with Organometallic Reagents:  A New Formal Aza Functionalization of Cyclopentadiene

Abstract

An unprecedented regioselective and anti stereoselective asymmetric ring opening of 1,3-cyclopentadiene-heterodienophile cycloadducts, including also 2,3-diazabicyclo[2.2.1]heptenes, with hard alkylmetals and copper-phosphoramidite catalysts, is reported. The induced ring opening, in conjunction with C-C bond formation, gives a catalytic and practical access to new heterofunctionalized cyclopentenes in an enantioenriched form (up to 86% ee). [reaction: see text]

Palladium/Lewis Acid‐Catalyzed Reactions of Bicyclic Hydrazines with Organostannanes: A General Methodology for the Stereoselective Synthesis of 3,4‐Disubstituted Cyclopentenes

“…Since the completion of this work, an article by Pineschi et al [22] has appeared which describes the catalytic asymmetric ring opening of 1,3-cyclopentadiene-heterodienophile cycloadducts with dialkylzinc and trialkylaluminium reagents in the presence of copper-phosphoramidate catalyst. According to their report, the copperphosphoramidate-catalyzed reaction of 3-azaoxabicyclo[2.2.1]-hept-5-enes with dialkylzinc afforded trans-1,2-hydroxamic acid.…”

Stereoselective Ring Opening of Bicyclic Nitroso Diels-Alder Cycloadducts with Carbon Nucleophiles

“…To our delight, the combination of copper salts and phosphoramidite ligands promoted the addition of dialkylzinc reagents to the double bond of NDA cycloadducts 1f and 1g, with cleavage of the C-O bond accompanied by allylic rearrangement (path a, Scheme 9), none of the product arising from attack of the organometallic species at the bridgehead carbon atom was detected (path b, Scheme 9). It should be noticed that in this way is possible to obtain the trans-1,2-hydroxamic acids of type 3 (R= Me, Et, Bu) with complete regioselectivity and anti-stereoselectivity [50]. Corresponding blank reactions performed without the use of phosphoramidite ligands gave a mixture of products and a very low conversion showing an evident ligand accelerated catalysis effect.…”

Hetero‐Diels‐Alder‐Reaktionen von Nitrosocarbonylverbindungen als nützliches Verfahren in der organischen Synthese

“…[114] Eine ähnliche Reaktivität wurde bei der Reaktion der bicyclischen Cycloaddukte 67 mit Dialkylzinkreagentien in Gegenwart von Kupferkatalysatoren beobachtet. [115,116] Wenngleich ein Angriff an der Carbonylfunktion gemäß den Un- tersuchungen von Keck zu erwarten wäre, [85] wurden keine durch einen Angriff an der "A"-Position gebildeten Produkte beobachtet. Erneut macht dies wahrscheinlich die Schwä-chung der C-O-Bindung in einer metallkoordinierten Spezies, zum Beispiel in Komplex 93, deutlich.…”