Advances in the synthesis and reactivity of phosphinines

• Main Author: Mao, Yanli
• Other Authors: Franck Alexis Chollet
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Science
• Online Access: http://hdl.handle.net/10356/51273
• Institution: Nanyang Technological University

The [4+2] cycloaddition reaction between methylenechlorophosphine pentacarbonyltungsten complex and furan compounds have been investigated in depth. Subsequent treatment of cycloadducts generated from monosubstituted furans with BBr3 and triethylamine affords the corresponding 2-hydroxy or 2-bromophosphinine derivatives. Under the same reaction conditions, the cycloadduct from 2,5-diphenylisobenzofuran yields 2-phosphanaphthalene, whose structure has been confirmed by X-ray analysis of its molybdenum complex. Decomplexation of 2-phosphaphenol by DPPE leads to the free parent 2-phosphaphenol, which is further silylated and acylated at the oxygen atom with retention of the aromatic structure. Moreover, it displays an effective coordination abilities with lower oxidation state metals like CuI, AuI, and Ru(DPPE)2Cl2. The phosphaphenol W(CO)5 complex also can be silylated, acylated, and triflated at the oxygen. However, whether alkylation occurs at O or P depends on the size of the electrophiles. P-alkylation with methyl iodide predominantly generates the 1-methyl-2-keto-1,2-dihydrophosphinine complex, whereas bulky isopropyl iodide exclusively affords the corresponding phosphinine ether under the same reaction conditions. The [4+2] cycloadduct between the 1-methyl-2-keto-1,2-dihydrophosphinine pentacarbonyltungsten complex and dimethylacetylenedicarboxylate can be used as a precursor for the methylphosphaketene tungsten complex under UV irradiation at room temperature. Under these conditions, the phosphaketene complex easily loses CO to yield the methylphosphinidene complex. Highly reactive alcohols and primary alkylamines trap both the phosphaketene and the phosphinidene complexes. Less reactive phenol and bulky amines together with alkynes and conjugated dienes only trap the phosphinidene complex. The first phosphinine 2-carboxaldehyde was synthesized by reduction of an ester group using DIBAL and transformed into an alkene via a Wittig reaction without destruction of the phosphinine ring.