Application Of In Situ Functionalized Wittig Type Reagents In Organic Synthesis

Phosphonium salts and phosphonates are widely used in organic synthesis as the precursors of Wittig (Wittig-Horner) reagents. Generally, phosphonium salts are prepared via the reaction of a halide and triarylphosphine/trialkylphosphine; phosphonates are prepared via the reaction of a halide and trialkylphosphite. However, these protocols might encounter difficulty when the desired halide is not so readily available, because of the effect of the substituent. In these cases, highly functionalized phosphonium salts and phosphonates are not readily available. The functionalization of phosphonium salts or phosphonates may offer an efficient method to obtain complex phosphonium salts and phosphonates from simple, readily available starting materials. On the basis of the background, this dissertation focuses on the preparation and olefination of highly functionalized phosphonium salts and phosphonates from simple, readily available starting materials.1. Allene-mediated reactions have attracted much attention by the organic community, and the propargyl-allenyl isomerization has been a useful and efficient method to afford allenes in situ. We have developed a sequence of propargyl-allenyl isomerizations and electrocyclizations for the functionalization of phosphonium salts via simple starting materials, which may provide an efficient one-pot synthesis of polysubstituted vinylbenzenes and naphthalenes.2. We have developed a sequence of propargyl-allenyl isomerizations/michael addition and Wittig olefination from propargylic phosphonium salts, which may provide an efficient one-pot synthesis for polysubstituted thiophenes, pyrroles and cyclopentenes.3. We have demonstrated that the carbon-carbon σ-bond of β-carbonyl phosphonates can readily be cleaved and added to the carbon-carbon triple bond of arynes under extremely mild conditions. The present insertion reaction provided the corresponding2-acylbenzylphosphonates from the simple phosphonates, which were directly used in a one-pot Horner-type olefination reaction.