Novel Applications of Polyfunctionalised Organoboron and Nitroso Compounds

This thesis deals with the reactivity of dienylboronated compounds towards aryl- and carbonylnitroso derivatives. The first part of this focused on the reactivity of dienylboronate compounds with arylnitroso derivatives resulting in pyrrole or furan formation. The outcome and efficiency of the reaction is related to the boron substituents and the solvent used, thus giving pyrroles, boronated oxazines or nitrones. A one-pot strategy was then applied to synthesise oxazoline derivatives using nitrones as key intermediates. Theoretical, as well as experimental, works supported that the formation of the pyrrole via regioselective nitroso Diels-Alder reaction/rearrangement/borate elimination cascade process. Secondly, attention was focused on the reactivity of dienylboronate compounds with carbonylnitroso derivatives. The nature of the carbonylnitroso had a dramatic impact on reactivity and, for example, the product resulting from a nitroso-ene reaction was obtained with pinacol derivatives. This ene-species was further used as the key intermediate for the synthesis of different polycyclic compounds. Several one-pot multicomponent processes were developed, giving access to various heterocycles with a high functional and structural diversity

Regioisomeric and substituent effects upon the outcome of the reaction of 1-borodienes with nitrosoarene compounds

A study of the reactivity of 1-borodienes with nitrosoarene compounds has been carried out showing an outcome that differs according to the hybridization state of the boron moiety. Using an sp2 boron substituent, a one-pot hetero-Diels–Alder/ring contraction cascade occurred to afford N-arylpyrroles with low to good yields depending on the electronic properties of the substituents on the borodiene, whereas an sp3 boron substituent led to the formation of stable boro-oxazines with high regioselectivity in most of the cases, in moderate to good yields. 1H and 11B NMR studies on two boro-oxazine regioisomers showed that selective deprotection can be performed. Formation of either the pyrrole or the furan derivative is pH- and regioisomer-structure-dependent. The results obtained, together with previous B3LYP calculations, support mechanistic proposals which suggest that pyrrole, or furan, formation proceeds via oxazine formation, followed by a boryl rearrangement and an intramolecular addition–elimination sequence

Composés organoborylés polyfonctionnalisés et dérivés nitroso : nouvelles applications

Cette thèse présente la réactivité de diènes polyfonctionnalisés incorporant un atome de bore (diènes borylés) en présence de composés de type nitroso. La première partie est une étude de la réactivité des diènes borylés en présence de dérivés arylnitroso. Le produit formé ainsi que l'efficacité de la réaction est dépendant de la substitution sur l'atome de bore ainsi que du solvant utilisé pour la réaction. Suivant les conditions employées, la formation de composés avec différentes structures; pyrroles, oxazines substitués par un atome de bore, ou nitrones a été obtenue. Une stratégie one-pot a ensuite été développée pour la synthèse d'oxazolines utilisant la formation des nitrones en tant qu'intermédiaire. Des investigations théoriques et pratiques concernant le mécanisme de la formation du pyrrole ont été réalisées. La séquence expliquant la synthèse de cette structure est basée sur la cascade suivante; cycloaddition régiosélective (Nitroso Diels-Alder)/réarrangement/élimination du borate. La formation des composés de type nitrone n'a pas été totalement explicité. Des recherches sont actuellement en cours dans le but d'obtenir plus de détails sur le mécanisme mis en jeu. La deuxième partie de l'étude est orientée sur la réactivité des diènes borylés en présence de dérivés carbonylnitroso. Au contraire des dérivés arylnitroso, la nature du composé carbonylnitroso joue un rôle majeur sur la réactivité. Si le même type de réactivité engendrant la formation de pyrroles et d'oxazines substitués par un atome de bore a été observé dans certains cas, l'utilisation d'un composé carbonylnitroso étant assez pauvre en électrons génère la formation du produit issu d'une réaction nitroso-ène. Ce produit, issu de la réaction nitrosoène, a été utilisé comme intermédiaire clé pour la synthèse de différents produits polycycliques. Une séquence one-pot, multicomposants, Diels-Alder/allylboration a été optimisée donnant différentes structures suivant le dienophile et l'aldehyde employé. Dans le but de diversifier la chimie du produit résultant de la réaction nitroso-ène, une autre séquence a été mise au point utilisant la synthèse des pyrroles. Une voie multi-étape a permis la synthèse de nouvelles structures bicycliques incorporant une oxazine et un pyrrole.This thesis presents the reactivity of dienylboronated compounds towards arylnitroso and carbonylnitroso derivatives and its use in the synthesis of heterocyclic and polycyclics compounds. The first study focused on the reactivity of dienylboronate compounds with arylnitroso derivatives resulting in pyrrole or furan products. The outcome and efficiency of the reaction is related to the boron on the dienyl moiety and the solvent used. Using the certain conditions, pyrroles, boronated MIDA ester oxazines or nitrones could be obtained. A one-pot strategy was then applied to synthesise oxazoline derivatives using nitrones as an intermediate. Theoretical, as well as experimental, work has supported that the formation of the pyrrole was obtained by a regioselective nitroso Diels-Alder reaction/rearrangement/borate elimination cascade process. Details on the nitrone formation have not been clarified, but further investigations are on-going. Secondly, attention was focused on the reactivity of dienylboronate compounds with carbonylnitroso derivatives. Contrary to the arylnitroso species, the nature of the carbonylnitroso had a dramatic impact on reactivity. On the one hand, similar reactivity towards the formation of pyrroles and boronated MIDA ester oxazines was observed, however, by employing a higher electron-deficient carbonylnitroso species, the product resulting from a nitroso-ene reaction was obtained. Ene-product was used as the key intermediate for the synthesis of different polycyclic compounds. A multicomponent, one-pot, Diels-Alder/allylboration procedure was optimised to yield various structures depending on the nature of the dienophile and the aldehyde. To diversify the chemistry of the ene-product another sequence was designed using the pyrrole synthesis. A multi-step pathway was optimised to afford novel fused bicylic oxazine-pyrrole products

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

In the last few years, multicomponent reactions involving boron substituted 1,3-dienes have emerged as important tools in synthetic organic chemistry. The most significant recent results and developments obtained in this area are reported in this review

Generating Skeletal Diversity and Complexity from Boron-Substituted 1,3-Dienes and Enophiles

Boron‐substituted 1,3‐dienes participate in ene reactions to afford new functionalized synthetic intermediates. After evaluating several enophiles as partners, the resulting products have been engaged in multistep sequences involving first a Diels Alder/allyboration process. A variety of skeletally diverse and complex polycyclic heterocycles were thus synthesized, such as tetrahydro‐ 1H ‐isoindole‐1,3( 2H )‐diones, eight‐membered lactones or tricyclic spiro compounds

Access to Fused Pyrroles from Cyclic 1,3-Dienyl Boronic Esters and Arylnitroso Compounds

Complimentary to classical hydroboration and boron-Wittig reactions, a new, efficient access to cyclic 1,3-dienyl boronic esters has been developed via diene or triene metathesis. Subsequently, fused pyrroles were synthesized with a broad substrate scope from the reaction of cyclic 1,3-dienyl boronic esters with arylnitroso compounds using a one-pot hetero-Diels−Alder/ring contraction sequence