Access to novel small molecule scaffolds is of great importance to the field of medicinal chemistry, and recently there has been particular focus on forming scaffolds with high three-dimensionality due to such compounds' improved success within clinical trials. Rigid three-dimensional scaffolds are of particular interest, with bridged bi-and poly-cyclic architectures being of particular importance due to their frequently potent bioactivity and associated current synthetic interest. Ideally, such systems would also offer the ability to perform orthogonal functionalization so as to enable facile library synthesis. Natural products have historically proved a useful starting point for drug discovery, with up to 75% of drugs being derived from or inspired by molecules originating in nature. The alkaloid family in particular has proved an excellent source of CNS active compounds, which is an area of medicinal chemistry that continues to offer significant challenges. However, synthetic access to alkaloid structures is frequently limited by complex syntheses, with each route typically offering access to only a single ring system. Broader access to alkaloid-like chemical space is therefore highly desirable, and indeed access to such analogues has seen considerable recent interest. Biomimetic syntheses offer attractive approaches to such systems, with arguably the first example of this being Robinson's synthesis of tropinone 2 (Scheme 1a), which achieved this via a one-step double-Mannich reaction. However, such an approach has yet to be extended more broadly, despite potentially enabling a general conversion of easily accessed dialdehydes into complex natural product-like scaffolds. We considered that stereochemically rich 1,4-dialdehydes of type 3, which are readily available from Diels-Alder cycloaddition/oxidative cleavage sequences, might be attractive substrates in this respect. Indeed, such systems have seen use in reductive amination-based diversification to form systems of type 4 (Scheme 1b); however, their extension to double-Mannich reactions remains essentially unexplored. Overall, such an approach would represent a one atom ring expansion of simple alkenes, forming systems that appear attractive as scaffolds for derivatization into compound libraries. Scheme 1. Previous and current access to three-dimensional amine scaffolds from dialdehyde building blocks.