Asymmetric Hetero-Diels–Alder Reaction of Danishefsky’s Dienes with α-Carbonyl Esters Catalyzed by an Indium(III)–PyBox Complex

Abstract

An efficient catalytic enantioselective hetero-Diels-Alder reaction of Danishefsky's dienes with α-carbonyl esters using a chiral In(III)-pybox complex has been demonstrated. This protocol offers several advantages, including mild reaction conditions, relatively low catalyst loading, and good to excellent enantioselectivities. Furthermore, the absolute configurations of the new alkynyl-containing products were determined by CD spectra in combination with TD-DFT calculations.

Toward the Synthesis of Muironolide A: Synthesis and Structure of Heteroleptic Lanthanide–Terpyridine Complexes with 2‐Oxo Amides

“…[3][4][5] The www.eurjoc.orgchiral ligands included in this study are illustrated in Scheme 2. [12] Although the reaction conditions for each ligand were individually optimized, none of them afforded satisfactory enantioselectivity, with the best, L1, performing substantially better than the rest (40-50 % ee).…”

“…Of note, while the majority of reported acac complexes with lanthanides contain more than two units of the ligand, [14,12] only one pyacac unit is present in the Dy complex. This property is desirable for catalyst development, because it is indicative of a more defined, unambiguous substrate binding.…”

Vinyl Dihydropyrans and Dihydrooxazines: Cyclizations of Catalytic Ruthenium Carbenes Derived from Alkynals and Alkynones

“…A new synthetic strategy to access these relevant structures. based on ruthenium-catalyzed cyclization of N-tethered alkynals and alkynones (6), has been developed ( Table 3). Either the N-SO 2 Ar-protected alkynals 6 a,b or N-Boc-and N-Cbzprotected alkynals 6 c,d were smoothly converted into 2vinyldihydrooxazines (7 a-d) in moderate to good yields under the typical reaction conditions (Et 2 O as solvent).…”

“…[1] Their partially hydrogenated derivatives, for example, 3,4-dihydropyrans, [2] are interesting precursors for tetrahydropyrans [3] and glycals, [4] which are useful building blocks, particularly in carbohydrate chemistry. [5] Two main synthetic strategies have been exploited for the efficient preparation of 3,4-dihydropyrans and their 4,5benzoderivatives: a) hetero-Diels-Alder (HDA) reactions of aldehydes and Danishefskys diene, [6] thus affording the corresponding dihydropyran derivatives with high diastereoand enantioselectivities, and b) endo cycloisomerization of alkynols with catalytic metal vinylidenes (W, Rh, and Ru; Scheme 1). [7] Other attractive and useful unsaturated pyran derivatives, 2-vinyltetrahydropyrans, have been accessed through alkyne-, allene-, or allyl-activated exo cyclizations using palladium, iridium, gold, and iron catalysts.…”

The Future of Catalysis by Chiral Lewis Acids

“…Box and pybox ligands continue to be popular ligands for asymmetric heteroDiels-Alder reactions, and examples include reactions catalyzed by InCl 3 (Scheme 12) [56] as well as an enantioselective version of a thia-HDA reaction Scheme 9 Chiral N,N 0 -dioxide-Ni(II) complexes catalyzed Diels-Alder reaction between 3-vinylindoles and methyleneindolinones [42] The Future of Catalysis by Chiral Lewis Acids [57]. Significant contributions have been made with the use of novel, but accessible, chiral N,N 0 -dioxide ligands using a wide spectrum of metal Lewis acids (Scheme 13) that provide very high stereocontrol for HDA and inverse-electron-demand HDA reactions [58][59][60][61][62][63][64][65].…”