Phospholene oxides, formation

As compared to the direct esterifications, the amidations had a lower enthalpy of activation (ca. 79 vs ca. 102 kcal/ mol) however, the amidations were significantly endothermic (33kcal/mol) [39]. It is recalled herein that the esterifications are thermoneutral [35]. As far as such amidation reactions are concerned, it is the fact that the MW-assisted reaction of phosphinic acids and amines is of limited use and the traditional method involving the reaction of phosphinic chlorides with amines still remains the method of choice (Scheme 5). During the preparation of l-amino-3-phospholene oxides (21) by this method, an interesting side reaction was also found to take place yielding a bis(phosphinoyl) amine (22) (Scheme 6) [40]. However, using appropriate molar ratios and addition techniques, both e formation of the amino-3-phospholene oxides (21) and that of the bis(products) (22) could be optimized [40]. 

C. Reactions not involving P=0 or P=S Groups.—Enamine phosphine oxides (45) have been prepared by the addition of amines to 1-alkynyl-phosphine oxides, and the reactions of their anions with various electrophiles have been reported. - With ketones a Wittig-type reaction leads to the formation of a/3-unsaturated ketones, in 53—70% yield, while with epoxides cyclopropyl ketimines are formed. A Diels-Alder reaction of l-phenyl-A -phospholen-l-oxide (46) with 1,4-diacetoxybutadiene has been used in the preparation of l-phenyl-benzo[/>]phosphole (47), as... 

To address this concern uretonimine-modified isocyanates with improved low-temperature properties were prepared using 4,4 -diphenylmethane diisocyanate catalyzed with 3-methyl-l-phenyl-3-phospholene-l-oxide. The formation of uretonimine was consistently higher than uretdione formation using this catalyst. The uretonimine-modified isocyanate can be stored at temperatures substantially lower than ambient temperature while still remaining liquid. In addition it is soluble in melted 4,4 -diphenylmethane diisocyanate. 

The stereochemistry of the addition has been recognized on the basis of structural features and chemical behavior of the complexes 9, produced in selected reactions of j with 1-ethoxy-1-oxo-2-phospholene 8. Neutralization of these complexes gave exclusively cis-3-substituted phospholane oxides J 0 while alkylation resulted in stereoselective formation of cis-3, cis- -disubstituted phospholane oxides JJ. The progress of the latter reaction was strongly dependent on the size of the alkyl groups involved. 

Bagi P, Kdllay M, Hessz D, Kubinyic M, Holczbauer T, Czugler M, Fogassy E, Keglevich G (2014) Resolution of l-n-propoxy-3-methyl-3-phospholene 1-oxide by diastereomeric complex formation using TADDOL derivatives and calcium salts of O, 0 -dibenzoyl-(2R,3R)-or O, 0 -di-P-toluoyl-(2R,3R)-tartaric acid. Tetrahedron Asymmetry 25 318-326... 

T. Novak, J. Schindler, V. Ujj, M. Czugler, E. Fogassy G. Keglevich, Resolution of 3-methyl-3-phospholene 1-oxides by molecular complex formation with TADDOL derivatives. Tetrahedron Asymmetry 17 (2006) 2599-2602. 

V. Ujj, P. Bagi, J. Schindler, J. Madarasz, E. Fogassy, G. Keglevich, A practical and efficient method for the resolution of 3-phospholene 1-oxides via coordination complex formation. Chirality 22 (2010) 699-705. 

The reaction is usually carried out at high temperatures (of about 200°C) in a polar solvent, such as tetramethylene sulfone, and the polyamide formation can be accelerated by the addition of l-phenyl-3-methyl-2-phospholene 1-oxide as catalyst. However, in the case of a two-step process, the reaction time of the first step must be carefully controlled, since the catalyst can also play a role in the formation of carbodiimides from two terminal isocyanate groups [36], These carbodiimides can then further react and lead to crosslinking [36], In most cases [34-39], the polymers are prepared with 4,4 -methylene bis(phenyl-isocyanate) (MDI), using adipic acid, isophtahc acid, azelaic acid, or a mixture of two of them (in order to accelerate the solubilization of the polyamide phase in the solvent) and a polyether based on tetramethylene oxide, ethylene oxide, or a mixture of propylene oxide and ethylene oxide. 

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