Studies On Synthesis And Reaction Of Allenes

Allenes are present in many natural products and have been showing very useful in organic synthesis, thus, much attention has been paid to allene chemistry. Nowadays, many strategies have been developed for the synthesis of different types of allenes. Synthetic utility in organic chemistry is another most important subject of allenes-various valuable products or intermediates have been synthesized based on the distinctive chemical properties of allenes. With our continuous interest in allene chemistry, we wish to realize some catalytic efficient methods for the synthesis of allenes and some catalytic asymmetric reactions of functionalized allenes. The whole dissertation may be divided into the following four parts:Part ?:CuI-catalyzed synthesis of functionalized terminal allenes1. We have developed an efficient catalytic method for the synthesis of functionalized terminal allenes from readily available substrates with a wide substrate scope and an excellent functional group tolerance. All reactions in this work are conducted on 10 mmol-scale.2. Based on this protocol, we developed two practical procedures for the synthetically useful basic reagent 2,3-butadien-1-ol on up to 10-g scales.Part ?:Palladium-catalyzed synthesis of multi-substituted allenes1. We have developed a general and efficient catalyst system consisting of o-(diphenylphosphino)benzaldehyde for the coupling reaction of propargylic carbonates with arylboronic acids. The catalyst system functions under very mild conditions and a variety of useful functional groups are compatible to afford multi-substituted allenes facilely.2. High efficiency of chirality transfer of propargylic carbonates is realized with the help of 2 equiv of water. Initial experiments demonstrated that the formyl group in the ligand has a significant impact in this coupling reaction.Part ?:Palladium-catalyzed asymmetric synthesis of axially multi-substituted chiral allenesAfter extensive screening, two sets of conditions have been identified to realize the kinetic resolution reaction of racemic propargylic carbonates with boronic acids in decent enantioselectivity and yields.Part ?:Palladium-catalyzed asymmetric coupling cyclization of N-(buta-2,3-dienyl)amidesWe have developed an enantioselective palladium-catalyzed coupling cyclization of N-(buta-2,3-dienyl)amides with aryl iodides for the efficient construction of new chiral oxazoline derivatives. After extensive research, we found that the (R,R)-ANDEN-Phenyl Trost ligand and benzene (solvent) performs better than others. By applying the easily accessible nature of starting materials and the compatibility of useful functional groups, a variety of different oxazolines may be synthesized facilely.