The Concept of Transient Chirality in the Stereoselective Synthesis of Functionalized Cycloalkenes Applying the Retro-Diels−Alder Methodology

Efficient Entry to the Hasubanan Alkaloids: First Enantioselective Total Syntheses of (−)‐Hasubanonine, (−)‐Runanine, (−)‐Delavayine, and (+)‐Periglaucine B

“…Conceptually related strategies have been previously applied using cyclopentadiene or anthracene as blocking groups. [14] However, in the absence of two activating substituents, retrocycloaddition reactions of these adducts require conditions (220-250 8C, diphenyl ether, or 400-500 8C, flash-vacuum pyrolysis) that were expected to be incompatible with functionalized advanced intermediates. By comparison, Diels-Alder adducts incorporating the 7-(trimethylsilyl)bicyclo[2.2.1]hept-2-ene substructure have been shown to undergo significantly faster retro-cycloaddition reactions.…”

Straightforward Synthesis of (R)‐(−)‐Kjellmanianone

“…[6] A retro-Diels ±Alder reaction [7] of 4 was the key step, resulting in virtually enantiopure 1. The six-step route started from optically active tricycle 5 (Scheme 1).…”

The Diels-Alder reaction: an update

“…A final introductory point illustrates a powerful synthetic strategy of Diels-Alder chemistry as a protecting group and temporary scaffold (or template), for the manipulation of the sensitive multiple functionalities of diene or dienophile types. In this approach the sensitive diene or dienophile portions of the molecules are tied up with a convenient partner in a Diels-Alder reaction, the cycloadduct is then chemically modified in accordance with the synthetic plan and finally undergoes a retro Diels-Alder reaction to liberate the desired product 25 . For example, the cycloaddition product of a reactive a,b-enone function with cyclopentadiene, can be submitted to the required chemo-, regio-and stereoselective reactions, dominated in part by the expected endo-cycloadduct structure, before retro DielsAlder reaction unravels a much more complex product.…”