TOTAL SYNTHESIS OF 1-PHOSPHABICYCLO(4.4.0)DECANE AND DERIVATIVES
Abstract
A five-step preparation of the title compound is described, starting with triethylphosphite and 5-bromopentene. The product was initially isolated as either cis-1-benzyl-1-phosphoniabicyclo{4.4.0}decane bromide, its methiodide counterpart, or the corresponding cis-bicyclic phosphine oxide; the bicyclic phosphine was obtained by phenylsilane reduction of the oxide. The key step involved an intramolecular free-radical ring-closure on the primary phosphine obtained from reduction of diethyl 1-(3-butenyl)-4-pentenyl phosphonate. Six other proposed synthetic routes toward the title compounds are discussed in detail. Synthesis of phosphorinane systems is covered; alkylation of phosphonate esters and phosphonium salts is explored. Preparation of phosphorinane itself is reported in good yield. Starting and intermediate compounds were characterized by elemental analysis, ('1)H and ('13)C NMR spectroscopy, and mass spectrometry. The bicyclic title compounds were additionally characterized by ('31)P NMR spectroscopy. Carbon-13 NMR data is reported for over 95 cyclic and acyclic organophosphorus molecules; comparisons with other similar systems are made. A new Karplus-like relationship between the dihedral angle of the lone-pair orbital on phosphorus and the (beta)-carbons is proposed. The maximum ('2)J(,PC) value occurs at small angles; smaller coupling constants arise from angles greater than 90(DEGREES). The stereochemistry of the title compounds was established by ('13)C NMR spectroscopy; the cis isomers always predominate over the trans in the successful synthetic scheme. Attempts to equilibrate the cis and trans bicyclic phosphines and phosphine oxides under a variety of conditions are described. In no case was isomerization observed. The conformational barrier in cis-1-phosphabicyclo{4.4.0}decane is estimated by computer-assisted ('31)P NMR analysis, and compared to the carbocyclic analog. Alkaline hydrolysis of 1-methoxy-1-phosphoniabicyclo{4.4.0}decane hexafluorophosphate was explored under both homo- and heterogeneous conditions. The trans isomer reacted with complete inversion of configuration about phosphorus; the cis isomer afforded a 2:1 mixture of inversion:retention products. Alkaline hydrolysis with isotopically enriched O-18 base showed full incorporation of the label. An explanation for the isomer-dependent stereospecificity is advanced. Alkaline hydrolysis of cis-1-benzyl-1-phosphoniabicyclo{4.4.0}decane bromide under both homo- and heterogeneous conditions was found to occur with predominant retention of configuration.
Recommended Citation
COWLES, JOHN MCGUIRE, "TOTAL SYNTHESIS OF 1-PHOSPHABICYCLO(4.4.0)DECANE AND DERIVATIVES" (1983). Dissertations (1962 - 2010) Access via Proquest Digital Dissertations. AAI8317273.
https://epublications.marquette.edu/dissertations/AAI8317273