Facile regio- and stereoselective total synthesis of racemic aklavinone

Recent advances in the Hauser annulation.

Discovered in 1928,1 the Diels–Alder reaction, ie the [4 + 2] cycloaddition of a diene (I) and a dienophile (II) or (IV) (Scheme 1), has become, arguably, the most powerful carbon-carbon bond forming process It is therefore surprising that the last comprehensive survey of the Diels–Alder reaction dates back to 19722 Since then, substantial gains in insight and methodology have been accomplished handin-hand with a body of creative and conceptually new applications in organic synthesis In view of the extensive literature, this chapter is limited to the formation of ‘all-carbon’ six-membered rings via bimolecular additions of 1,3-dienes to alkenes and alkynes

Intermolecular Diels–Alder Reactions

Reactions of acyl anion equivalents derived from cyanohydrins, protected cyanohydrins and α-dialkylaminonitriles

Total Synthesis of Dimethyl Sulfomycinamate

The addition of stabilized nucleophiles to activated π-systems is one of the oldest and most useful constructive methods in organic synthesis, dating back more than a hundred years. In 1887 Michael, after whom the most well-known example of this reaction was named, published the first of a series of papers on this reaction describing the addition of the sodium salt of both diethyl malonate (1) and ethyl acetoacetate (2) to ethyl cinnamate (3) to give the products (4) and (5), respectively (equation 1).1 This Michael reaction, in which a carbanion stabilized by one or usually two electron-withdrawing groups adds to the β-carbon of an α,β-unsaturated carbonyl derivative, represents one of the earliest and most highly utilized methods for carbon–carbon bond formation. In that same 1887 paper,1a Michael also reported the synthesis of triethyl cyclopropane-1,1,2-tricarboxylate (9) from (1) and ethyl α-bromoacrylate (6) via the intermediates (7) and (8), a synthetic route to cyclopropanes used often today (Scheme 1). In 1894 he showed that an alkynic ester could also function as the electrophilic component in these reactions, e.g. (1) and (10a) or (10b) giving (11a) or (11b), respectively (equation 2).2 This reaction and its variants were in wide use around the turn of the century to prepare straight chain polycarboxylates, e.g. the reaction of (12) to give (13; equation 3) and cyclohexane-1,3-diones, e.g. (15; equation 4) (via Knoevenagel and Claisen condensations).3 The combination of Michael addition followed by intramolecular aldol condensation and decarboalkoxylation furnishes cyclohexenones, e.g. isophorone (17; equation 5), from enones such as mesityl oxide (16) and the salt of ethyl acetoacetate (2).4 This process of annulation was made much more general in the 1930s by Robinson and his coworkers,5 who showed that vinyl ketones and their derivatives, e.g. Mannich bases, could be used with simple ketone enolates to produce cyclohexenones of a wide variety, e.g. (20; equation 6), a process which has come to be known as the Robinson annulation.6

Facile regio- and stereoselective total synthesis of racemic aklavinone

Citations

Recent advances in the Hauser annulation.

Intermolecular Diels–Alder Reactions

Reactions of acyl anion equivalents derived from cyanohydrins, protected cyanohydrins and α-dialkylaminonitriles

Total Synthesis of Dimethyl Sulfomycinamate

Stabilized Nucleophiles with Electron Deficient Alkenes and Alkynes

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