Reakcije alena i nukleofila katalizovane paladijumovim kompleksima

Abstract

U sklopu ove doktorske teze proučavane su transformacije alena u prisustvu paladijumovih kompleksa, a posebno reaktivnost π-alil-paladijumovih intermedijera generisanih iz alena u reakcijama sa heteroatomskim nukleofilima. Reakcije alena i aril- ili vinil-halogenida u prisustvu paladijumovih kompleksa sa acetatom kao nukleofilnom vrstom omogućava direktan pristup strukturno kompleksnim alilnim acetatima. Alilni acetati predstavljaju korisnu klasu organskih jedinjenja koja se u velikom obimu upotrebljavaju za reakcije alilnih alkilovanja katalizovanih prelaznim metalima. Oni su, takođe, veoma značajni za dobijanje γ-nezasićenih derivata karboksilnih kiselina jer učestvuju u reakcijama 3,3-sigmatropnog premeštanja Claisen-Ireland-ovog tipa, dok hidrolizom mogu dati i sintetski veoma važne alilne alkohole. Mada su i sami alilni acetati supstrati za paladijumom katalizovane reakcije, razvijeni su uslovi koji omogućavaju sintezu ove klase jedinjenja u dobrim prinosima. Reakcijom nesimetričnih alena sa aril- ili vinil-halogenidima, nastaje π-alil-paladijumov intermedijer, koji u reakciji sa acetatnim anjonom generalno daje smešu regioizomernih acetata koji se mogu razdvojiti. U nekim slučajevima, gde dominira sterni faktor, dobijen je samo jedan regioizomer vezivanjem nukleofila za sterno manje zaštićenu stranu π-alil-paladijumovog intermedijera. Regiohemijski ishod reakcije proučavan je i u intramolekulskim reakcijama, gde je pokazano da uslovi koji se uobičajeno koriste favorizuju nastajanje termodinamički stabilnijeg proizvoda sa endocikličnom dvostrukom vezom...

The aim of this thesis was to investigate reactivity of allenes in the presence of palladium complexes, particularly reactivity of π-allylpalladium intermediates, generated from allenes, and heteroatom nucleophiles. The reactions of allenes and aryl- or vinyl-halides in the presence of palladium complexes, with acetate as nucleophilic species, provide a direct access to structurally complex allyl acetates. Allyl acetates represent a useful class of organic compounds extensively used in the allylation processes catalysed by a range of transition metals. An additional important methodology, the Claisen–Ireland 3,3-sigmatropic rearrangement, employs allyl acetates or related esters to produce γ-unsaturated carboxylic acids and their derivatives. They can also be a source of synthetically very useful allyl alcohols via hydrolytic processes. Although the allyl acetate itself is a substrate for palladium-catalysed reactions, conditions allowing the synthesis of this class of compounds were developed furnishing the products in acceptable yields. Nonsymmetrical allenes in reaction with aryl or vinyl halides, via π-allyl-palladium intermediates, generally afforded a separable mixture of regioisomeric acetates. In some cases, where steric factors prevailed, a single regioisomer was obtained via the nucleophilic attack on the π-allylpalladium intermediate from the less sterically hindered side. The regioselectivity issue was also studied in intramolecular reactions. It was shown that conditions usually employed were in favour of the thermodynamically more stable product with the endocyclic double bond...