Phospholene 1-oxides synthesis

Fig. 2.1. Response surface for phospholene oxide synthesis (from Coieman etal. 1993, with permission of the Royai Society of Chemistry).

Polyhexamethylenecarbodiimide, an insoluble condensation reagent for the synthesis of peptides, is obtained in the reaction of hexamethylene diisocyanate with a phospholene oxide catalyst in NMP. The isocyanate end groups are reacted with ethanol. Linear polycarbodiimides, upon reaction with adipic acid, form polyureides. For example, reaction of the 2,4-TDI derived carbodiimide with adipic acid in DMF produces the polymer, mp295°C.222... 

Quin s group have reported the synthesis of a number of tricyclic phospholene oxides, e.g., (9), by the McCormack reaction. The isomeric bicyclic phosphine... 

The phospholene oxides resulting from the McCormack reaction also serve as highly useful starting materials for the synthesis of phospholane oxides by simple hydrogenation techniques (Equation (47)). 

A recently published example (Coleman et al. 1993) nicely illustrates the use of factorial design in chemical synthesis. The reaction of 1,1,1-tri-chloro-3-methyl-3-phospholene (1) with methanol produces l-methoxy-3-methyl-2-phospholene oxide (2) as shown in the reaction scheme. The experimental procedure involved the slow addition of a known quantity of... 

The treatment of isocyanates with 3-methyl-l-ethyl-3-phospholene-l-oxide (71) is a useful method for the synthesis of carbodiimides748 in good yields.749 The mechanism does not simply involve the addition of one molecule of isocyanate to another, since the kinetics are first order in isocyanate and first order in catalyst. The following mechanism has been... 

The dehydrogenation step can also be conducted on phosphole oxides and sulfides as illustrated with the synthesis of a series of previously unknown 1,3,4-triphenylphospholes. The starting material is l,3,4-triphenyl-3-phospholene-... 

The reduced phospholes are never made directly by hydrogenation of phospholes most commonly, the ring is created in the desired state of reduction while phosphorus is in the oxide or sulfide form, and the process is completed by removal of these atoms. For the synthesis of 2- and 3-phospholenes, the McCormack cycloaddition of trivalent phosphorus halides with dienes, followed by hydrolysis, is the method of choice for obtaining the requisite P-oxides. This process, first described in US patents <53USP2663737,53USP2663738) by W. B. McCormack of the duPont Co., has... 

Oxidative ring-opening of the bicyclic phospholenes (48 R = OH, Me, Ph) by ozonolysis affords the phosphonane diones (49 R = OH, Me, Ph), which were found to be valuable intermediates for the synthesis of other nine-membered rings <82JOC905,82JAI893). 

The next efforts were directed to obtain precursors of bidentate P-ligands. In connection with the synthesis of the precursor of LuPhos and its Pt complex [59], the addition of diphenylphosphine oxide to l-phenyl-2-phospholene 1-oxide (40) was studied under MW conditions. The MW-assisted addition of other >P(0)H species was also investigated. It was found that in most of the cases, the reaction was not selective xmder MW irradiation (Scheme 14). The traditional activation of the >P(0)H species by MesAl followed by the addition of the anion so formed led to "clean" reactions [60]. 

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