Due to the scarcity of energy resources that we are facing today, there is an increasing need for new methodology developments that are green and sustainable while minimizing unnecessary substrate pre-functionalization, by-product formation and waste generation. In this context, asymmetric rhodium-catalyzed hydroacylation is an atom-economical method for the preparation of chiral ketone derivatives from aldehyde and olefin precursors. This transformation is also applicable to keto-aldehyde precursors en route to chiral lactones. This dissertation describes the development of three specific methodologies, namely: 1) the synthesis of enantioenriched cyclopropyl ketones by enantio- and diastereoselective intermolecular rhodium-catalyzed hydroacylation of cyclopropenes, 2) the synthesis of enantioenriched phthalides by enantioselective rhodium-catalyzed intramolecular hydroacylation of ketones, and 3) the synthesis of tertiary branched allylic amines by silver-catalyzed ring-opening hydroamination of cyclopropenes.

Due to the scarcity of energy resources that we are facing today, there is an increasing need for new methodology developments that are green and sustainable while minimizing unnecessary substrate pre-functionalization, by-product formation and waste generation. In this context, asymmetric rhodium-catalyzed hydroacylation is an atom-economical method for the preparation of chiral ketone derivatives from aldehyde and olefin precursors. This transformation is also applicable to keto-aldehyde precursors en route to chiral lactones. This dissertation describes the development of three specific methodologies, namely: 1) the synthesis of enantioenriched cyclopropyl ketones by enantio- and diastereoselective intermolecular rhodium-catalyzed hydroacylation of cyclopropenes, 2) the synthesis of enantioenriched phthalides by enantioselective rhodium-catalyzed intramolecular hydroacylation of ketones, and 3) the synthesis of tertiary branched allylic amines by silver-catalyzed ring-opening hydroamination of cyclopropenes.

No description available.

A catalytic organometallic addition-ring opening sequence of cyclopropenes that enables the efficient and highly stereoselective synthesis of multisubstituted alkenes has been developed. A possible mechanism of organoaluminium reaction is proposed. The metalloenolate resulting from ring opening can be trapped with various electrophiles, enabling a rapid increase in molecular complexity in a one-pot operation. Also, in the presence of stoichiometric magnesium halides, a range of bis-activated cyclopropenes undergo highly stereoselective ring-opening reactions to produce multisubstituted alkenyl halides. The halogen nucleophile promotes Lewis-acid mediated regioselective SNVσ attack at the sp2-carbon of cyclopropene, resulting in the formation of acyclic conjugate enolate, which can be trapped with enones to furnish more highly functionalised products. At last, copper-catalysed asymmetric conjugate reductions of β,β'-disubstituted 2-alkenylheteroarenes are reported. A range of nitrogen-containing aromatic heterocycles are able to provide effective activation of an adjacent alkene for highly enantioselective catalytic conjugate reduction reactions. Extension of the general concept to other classes of heteroarenes has been proven successful. Further manipulation of the condition is required to tolerate more hindered heteroarene substrates.

No description available.

No description available.

Activated cyclopropanes have been extensively used in synthetic chemistry as precursors for cycloaddition reactions. The rationale behind this is their ability to undergo ring-opening when activated by a Lewis acid, this can be enhanced further by the presence of a carbocation stabilising group like electron-rich aromatics. The stabilised dipole formed after ring opening can be trapped with suitable electrophiles such as imines and aldehydes via a [3+2] cycloaddition reaction. This results in the synthesis of pyrrolidines and tetrahydrofurans in excellent yields but moderate diastereoselectivity. Similarly, 6-membered heterocycles can be formed via a [3+3] cycloaddition reaction of activated cyclopropanes with nitrones. Now to extend the scope of the methodology, a [3+3] dipolar cycloaddition has been developed using activated 2,3 disubstituted cyclopropane diesters to access a range of highly functionalised oxazines in moderate to good yields (50-75%) and with reasonable diastereoselectivity. The use of activated symmetrical disubstituted cyclopropanes afforded the desired oxazines in a regio- and diastereocontrolled manner, while the use of unsymmetrical cyclopropanes significantly reduced the diastereoselectivity of the reaction. The stereochemistry outcome of the reaction developed was determined by nOe analyses and X-ray diffraction structures could be recorded in some examples. A new methodology has also been developed to gain access to novel N-heterocyclic- and phenol- substituted cyclopropanes in one step from the corresponding cyclopropene via a conjugated addition.

Natural products and small molecules play a major role in drug development. However, using natural products as a source of medicine comes with many challenges, such as lack of natural abundance and difficulty in isolation. Consequently, synthetic organic chemistry is a solution in order to access these compounds in usable quantities. However, synthetic chemisty comes with its own challenges such as efficiency, chemoselectivity, stereoselectivity and enantioselectivity. Therefore, synthetic tools that addresses these challenges are required solve these limitations. This thesis discusses new methodologies using strained carbocycles (cyclopropanes and cyclopropenes) as the reactive subunit for the construction of different carbocyclic and heterocyclic compounds. The homo-Nazarov cyclization of alkenyl and heteroaryl cyclopropyl ketones was used in order to construct cyclohexenones, cyclohexenols, heteroaryl ring-fused cyclohexenones, dihydrofurans, furans and furanones in a mild and efficient manner. Benzofused heteroaromatic compounds were achieved via the Lewis acid-catalyzed cycloisomerization of cyclopropene-3,3-dicarbonyls and furan-3-carboxylates. These heteroaromatic compounds can be applied to medicinal chemistry and material science.

The thesis is divided into three chapters Chapter 1¡BFlash vacuum pyrolysis of 2-chloro-N-arenylideneaniline gave quinolines by the intromolecular cyclization. And then, flash vacuum pyrolysis of 2-methoxy-N-arenylideneaniline gave the benzothiazole products by the bond cleavage and the radical reaction. Chapter 2¡BFlash vacuum pyrolysis of 32 gave Stemofuran C. And then, flash vacuum pyrolysis of 33 gave 31 which belonging to the former compound of E6 reported on the paper. We also found that we also could get 2-phenylbenzofuran by flash vacuum pyrolysis of 44. Chapter 3¡BFlash vacuum pyrolysis of furylmethyl benzoates¡Bbenzo- thienylmethyl benzoates and N-methylpyrrolylmethyl benzoates gave the corresponding products by the interconversion between vinylcarbene and cyclopropene.

No description available.