Development of novel transition metal-catalyzed and organocatalytic transformations.

The design of new reactions and synthesis strategies is a central focus of modern synthetic organic chemistry that facilitates the construction of complex molecules, which are hardly accessible by previous methods. One of the topics discussed in the thesis is the development of transition metal-catalyzed additions of metallic entities to cyclopropenes. This newly developed protocol allow for the short and efficient synthesis of a variety of cyclopropyl silanes and germanes. Moreover, the scope of the previously reported Pd-catalyzed sila- and stannastannation reaction of cyclopropenes was significantly broadened. It was shown that employment of Pd(OAc)2, in combination with bulky 2,6-dimethylphenylisocyanide, allowed for highly diastereo- and regioselective dimetalation of up-to-trisubstituted cyclopropenes, which were problematic substrates under the previously reported catalytic conditions. It was also shown that the addition of metallic species is generally controlled by the steric factors and proceeds from the least hindered face of the cyclopropene. We also developed a novel organocatalytic Sila Morita-Baylis-Hillman reaction of 1-silylcyclopropenes. This novel cascade transformation features 1,3-Brook rearrangement/elimination sequence and allows for the direct and efficient preparation of valuable siloxymethylenecyclopropenes, not easily available via existing techniques. The reaction was shown to be extremely general with respect to the carbonyl component: a broad range of differently substituted aryl and alkyl aldehydes, as well as activated ketones, were shown to efficiently participate in this reaction. Moreover, application of this methodology to the silylated arylvinyl ketones allowed for the preparation of the corresponding silylated MBH adducts, which are not available via the traditional MBH-reaction. We also developed an efficient approach towards alkynyl epoxides. This novel protocol utilizes alkynyl halides as both source of halonium and acetylide in the same transformation.