Aluminum Acetals in Organic Synthesis

Abstract

Aluminum acetals are easily obtained from esters and lactones by reduction with aluminum hydrides. These thermally unstable tetrahedral intermediates have found applications in organic synthesis, with various methodologies taking advantage both of the stabilities of these aluminum species at low temperatures and of their tendencies to undergo rearrangement into the corresponding aldehydes. Efficient one‐pot transformations can be achieved from aluminum acetals under ionic and radical conditions. A comprehensive overview of the reactivity of these species, including the most recent advances in this field, is presented in this microreview.

Cationic aluminum hydride complexes: reactions of carbene–alane adducts with trityl-borate

“…Aluminum hydrides are important reagents in organic, inorganic and materials chemistry. Indeed, such species are used in a variety of roles including reagents for reductions [1][2][3][4][5][6] and in inorganic synthesis. 7,8 Applications as components in materials chemistry and in particular, hydrogen storage materials [9][10][11] have also garnered attention.…”

Synthesis of Polysubstituted γ‐Butenolides via a Radical Pathway: Cyclization of α‐Bromo Aluminium Acetals and Comparison with the Cyclization of α‐Bromoesters at High Temperature

“…The sequence is based on the reactivity of the cyclic aluminium acetals formed as products of the radical cyclization. These aluminium species were found to react with nucleophiles, but they could also transfer a hydride onto the carbonyl group of a ketone or an aldehyde 19. The Oppenauer‐type oxidation of the cyclic aluminium acetals proved to be very efficient for the preparation of γ‐lactones from α‐bromoesters.…”

“…These aluminium species were found to react with nucleophiles, but they could also transfer ah ydride onto the carbonyl group of ak etone or an aldehyde. [19] The Oppenauer-type oxidation of the cyclic aluminium acetals provedt ob ev ery efficient for the preparation of g-lactones from a-bromoesters. Only at wo-to threefold excesso facheap, commercially available aldehyde was required to perform the oxidation in situ and obtain g-lactones in high yields, as previously illustrated by the synthesis of (À)-trans-cognac lactone (Scheme 9).…”

Improved Synthesis of Anxiolytic, Anticonvulsant, and Antinociceptive α2/α3-GABA(A)-ergic Receptor Subtype Selective Ligands as Promising Agents to Treat Anxiety, Epilepsy, and Neuropathic Pain

“…The reported mechanism is straightforward. 43,44 The hydride from PDBBA attacks the carbonyl carbon forming a tetrahedral intermediate, and the elimination of the ethoxy group yields the desired aldehyde.…”