Palladium‐Catalyzed Formation of Cyclic Ethers – Regio‐, Stereo‐ and Enantioselectivity of the Reaction

Abstract

An efficient and stereoselective synthesis of 3‐alkyl‐3‐hydroxymethyl‐5‐vinyltetrahydrofurans is described by the Pd0‐catalyzed cyclization of the methyl carbonates of ω,ω‐bis(hydroxymethyl)‐α,β‐unsaturated alcohols. The use of chiral ligands gave the corresponding THF derivatives in low to moderate enantiomeric ratios. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Diastereoselective synthesis of 2-vinylpyrrolidines and 2-vinylpiperidines by the palladium-catalysed cyclization of amino-allylic carbonates containing a chiral protecting group

“…This type of transformation frequently occurs under mild conditions, tolerates a broad array of functional groups, and proceeds with high stereoselectivity. Extending our previous work on the use of allylic carbonates in the synthesis of O-and N-heterocycles, [35][36][37][38][39][40] in this paper we report new results on diastereoselective intramolecular Pd(0)-catalysed allylic aminations. Herein, we present the first examples of asymmetric palladium catalysis in which the starting amino carbonates contain a chiral protecting group with known and specified absolute configuration which can act as a chiral auxiliary and also enable one to perform the cyclization reaction in a stereoselective way, without the presence of any chiral ligands.…”

π‐Helicenes Truncated to a Minimum: Access Through a Domino Approach Involving Multiple Carbopalladations and a Stille Coupling

“…The triple bond in 10 / 11 was generated with the Bestmann–Ohira reagent 9 , starting from the corresponding carbaldehyde 15. The bromine‐containing congener 10 was elongated through attachment of 8 16 to the respective propargylic iodide, whereas the iodine‐substituted analogue 11 was reacted with dimethylmalonate. Iodine–magnesium exchange paved the way for the attachment of the stannyl group to furnish 15 .…”

“…To explore the scope of this domino cascade, the reaction conditions were then applied to a range of substrates (16)(17)(18) with two, three, or four triple bonds embedded in the chain between the arene moieties (Table 1). In all cases, the respective all-Z oligoenes (19)(20)(21) were obtained.…”

Organoselenium-Catalyzed Synthesis of Oxygen- and Nitrogen-Containing Heterocycles

“…1 This is a modified literature procedure. 9 A 25 mL round-bottom flask equipped with a stir bar was charged with 7g (296 mg, 1.2 mmol) and anhydrous DCM (10 mL). The colorless solution was cooled to 0 ºC , then pyridine (193 μL, 2.4 mmol) and n-propyl carbonochloridate (146 μL, 1.3 mmol) was added.…”