Une nouvelle voie d’accès à des structures tri-cycliques originaux les « oxazino-indole di-iodés» a été mise au point à partir des acides 1H-indole-2-carboxyliques commerciaux ou des acides 1H-indole-2-carboxyliques fonctionnalisés obtenus par la réaction d’Hemetsberger-Knittel. La dernière étape de cette séquence est une réaction d’iodocyclisation qui s’est avérée totalement régio- et stéréosélective selon un processus de type 6-exo-dig. Cette méthodologie a ensuite été étendue en série isoindolique permettant un accès à des motifs « oxazino-isoindolique di-iodés » originaux. Afin d'étendre davantage cette méthodologie, de nouveaux « oxazepino-indole di-iodés » ont été préparés en utilisant la même approche synthétique à partir de l'acide 1H-indole-7-carboxylique. La réactivité des structures tri-cycliques di-iodés a été étudiée via des réactions de Cross-Coupling (Stille, Sonogashira, Suzuki) par l’utilisation de sels de palladium permettant une fonctionnalisation régiosélective de l’iode exocyclique. / A new access pathway to the original tricyclic structures "di-iodinated oxazino-indole" was developed from the commercial 1H-indole-2-carboxylic acids or functionalized 1H-indole-2-carboxylic acid obtained by Hemetsberger-Knittel reaction. The last step in this sequence is an iodocyclisation reaction that is proved to be completely regio- and stereoselective via 6-exo-dig process. This methodology was then extended to isoindolic series allowing access to original "di-iodinated oxazino-isoindole" motifs. To further extend this methodology, new"di-iodinated oxazepino-indoles" were prepared using the same synthetic approach from the 1H-indole-7-carboxylic acid. The reactivity of the di-iodinated tri-cyclic structures has been studied via Cross-Coupling reactions (Stille, Sonogashira and Suzuki) by the use of palladium salts allowing a regioselective functionalization of the exocyclic iodine.

This thesis is concerned with the development of transannular iodoamination methodology for the synthesis of pyrrolizidine, indolizidine and tropane alkaloids. Chapter 1 introduces the concept of a ‘transannular cyclisation’ and outlines the utility of such cyclisations in the synthesis of a range of [x.y.z]-azabicyclic alkaloids. Chapter 2 describes the development of a three step lithium amide conjugate addition, ring-closing metathesis and transannular iodoamination protocol for the preparation of the pyrrolizidine scaffold ([3.3.0]-azabicycle). Cyclisation of a hexahydroazocine occurs with concomitant N-debenzylation to give a single diastereoisomer of the corresponding C(7)-iodopyrrolizidine product, which is then elaborated to the known pyrrolizidine, (−)-7a-epi-hyacinthacine A1. Chapter 3 delineates an extension of the methodology described in Chapter 2, and an investigation into accessing alternate diastereoisomeric pyrrolizidine scaffolds via the transannular iodoamination process. These studies culminate in the synthesis of two pyrrolizidine alkaloids, (−)-hyacinthacine A1 and (−)-hyacinthacine A2. Chapter 4 details investigations into the further elaboration of the C(7)-iodopyrrolizidine scaffold synthesised in Chapter 2. A nucleophilic displacement reaction with azide leads to the synthesis of novel 7-deoxy-7-aminoalexine analogues, whilst radical-mediated substitution of the iodide by oxygen allows the synthesis and isolation of the pyrrolizidine alkaloid (−)-1-epi-alexine. Chapter 5 outlines the development of the transannular iodoamination reaction to facilitate the synthesis of the tropane architecture ([3.2.1]-azabicycle). A tandem lithium amide conjugate addition and aldol reaction sequence is followed by ring-closing metathesis to give the required aminocycloheptene. Subsequent treatment with iodine results in transannular cyclisation to give a single iodotropane product which, following elaboration culminates in the synthesis of (+)-pseudococaine. Chapter 6 contains full experimental procedures and characterisation data for all compounds synthesised in Chapters 2, 3, 4 and 5.