Photooxygenation of Furylalkylamines: Easy Access to Pyrrolizidine and Indolizidine Scaffolds

Abstract

A highly adaptable method targeting the ubiquitous and very important pyrrolizidine and indolizidine scaffolds is presented. The general synthetic utility of the method is underscored by its application to the rapid and easy synthesis of five natural products starting from readily accessible alkylfuran precursors. These unprotected primary furylalkylamines are subjected to photooxygenation conditions, which initiate a complex cascade reaction sequence concluding with the production of high value motifs. This sequence can be tailored to need by varying the choice of both photosensitizer and base additive.

One‐Pot Synthesis of Diverse γ‐Lactam Scaffolds Facilitated by a Nebulizer‐Based Continuous Flow Photoreactor

“…Following the success of the intermolecular reaction sequences, we next sought to add a second oxidation step to the reaction sequences (reaction sequences of type C, Scheme ). This unique second oxidation, facilitated by methylene blue and this time using ground state oxygen ( 3 O 2 ),, is beneficial as it can be used to introduce further functionality (such as, an extra degree of unsaturation) to the products; thus, enhancing their range and potential utility. The results are presented in Table ( 1 → 6 – 9 ).…”

A Novel Nebulizer‐Based Continuous Flow Reactor: Introducing the Use of Pneumatically Generated Aerosols for Highly Productive Photooxidations

“…The rates of the reactions of 1 O 2 with a broad range of functional groups (or even the same functional group substituted to a different degree; for example, a di‐ versus a monosubtituted furan both found within the same molecule) are such that differentiation is very easily achieved. In addition, 1 O 2 does not react with alcohols and can be used in the presence of unprotected amines, thus rendering protecting groups essentially redundant, quite unlike a large number of other oxidants. Finally, the number of methodologies using singlet oxygen is currently multiplying very rapidly because 1 O 2 can be used to initiate high‐yielding cascade reaction sequences which involve rapid and dramatic increases in molecular complexity, a characteristic which both represents step economy and facilitates access to new chemical space .…”

Elucidating the mass spectrum of the retronecine alkaloid using DFT calculations

“…According to the ring substitution and saturation of the compound, alkaloids also show biological activities in glycosidase inhibition, pulmonary hypertension, and hepatotoxicity, being a very attractive and challenging target for synthetic chemists to develop new methodologies …”