Phospholenes reactions with

Biphilic Reactions with Dienes or Carbonyl Compounds. Stereochemical details have appeared of the reactions between substituted 1,3-dienes and halogenophosphines, such as dichloromethylphosphine (21a) and dibromo-phenylphosphine (21b). In general, both cis- and /ra/i5-adducts are formed, and they are not interconvertible via quinquecovalent intermediates. The conversion of these adducts to A -phospholens or to A -phospholen-l-oxides produces cis-trans mixtures. 

The reaction of the phospholen (65) with aromatic acid chlorides in the presence of triethylamine, followed by addition of DaO, gives a ready route to aromatic [1-2H]-aldehydes with 100% incorporation of deuterium.55... 

Symmetrical carbodiimides, i.e., molecules with the same substituent on both nitrogen atoms, are best prepared from alkyl or aryl isocyanates in the presence of a phospholene oxide catalyst, the byproduct being carbon dioxide gas. No solvent is required for this reaction. Unsymmetrical carbodiimides or alkylarylcarbodiimides are also obtained from isocyanates, either by reaction with amines and subsequent dehydration of the intermediate... 

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... 

Macromolecules with carbodiimide linkages in their repeat units are obtained from aliphatic and aromatic diisocyanates using a phospholene oxide catalyst. However, instead of linear polymers, only crossUnked thermosets are obtained in this manner. In contrast, linear polymers with pendant carbodiimide units are obtained from poly(vinyl azide) by subsequent reaction with triphenylphosphine to formpoly(phosphine imines) followed by reaction with monoisocyanates to generate the Unear poly(carbodiimides). 

Model studies for the syntheses of phosphonate analogues of sphingomyelin and ceramide 1-phosphate from pentaco-ordinate phospholene 112 have been reported. Compound 112 undergoes ring opening on reaction with dialkyl azodicarboxylates to give 113 which reacts with sodium borohydride stereoselec-tively to give predominantly trans- 4 (Scheme 6). The preparation has been described, via phosphorus chloride methods, of the potential haptens 115 for the production of phospholipase A2-like catalytic antibodies. ... 

Studies of the kinetics of the reactions of A -phospholens (108) with diethyl peroxide are consistent with a mechanism involving rate-determining biphilic attack of the phospholen on the peroxide, followed by a fast fragmentation of the intermediate phosphorane. " ... 

Thionophosphenous Acid Esters and Amides. Another ring system that we have found (75) to serve as a precursor of low-coordination species is the 7-phosphabicyclo[2.2.1]heptene system (also known as 7-phosphanorbomene). We have used this sytem for the thermal generation of derivatives of two previously unknown 2-coordinate species, the thionophosphenous amides 12 and the thionophosphenites 13 (Scheme 3). These species are trapped by a cycloaddition reaction with a diene to form the 5-membered 3-phospholene ring, as shown for 12. 

The order of reactivity MeOPCla > (63) > (EtO)2PCl > (MeO)3P has been found for addition to isoprene. This diene and the phosphites (75) gave only the phospholens (76). If phosphoranes are intermediates in these reactions, then the fate of the aromatic nucleus is of some interest. The phospholens (77) with diethyl peroxide gave isoprene and diethyl phenylphosphonite, presumably via the phosphorane. ... 

The lack of success in the preparation of 2,3-epoxy derivatives from 2-phospholenes has been obviated by the use of the halohydrin procedure. Thus, the treatment of the 2-phospholene 351 (R = Et, R = Me) with nba yields a stereoisomeric mixture of the halohydrins 366 which, when treated with KOAc in acetone, in turn, yields a mixture of two stereoisomers of the epoxide 367. The product from the same reaction with the corresponding 3-phospholene is identical with that obtained by the direct oxidation of the phospholene, and is therefore thought to have structure 368. ... 

Phospholenes 195 with P-F bond are prepared by the reaction of 1,3-dienes with fluorophosphates. 

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... 

Thioalcohols could also be used as reaction components with l-hydroxy-3-phospholene oxides (7 and 8) xmder MW conditions. It was not a sxuprise that the products were thioesters (17) and not esters (9/10) (Scheme 4) [38]. Hence, indeed the alcohol/thioalcohol is phosphinoylated by reaction with the cyclic phosphinic acid and not the phosphinic acid is alkylated by the alcohol or thioalcohol. Quantum chemical calculations revealed that the esterification with thioalcohols is rather endothermic (48.5kJ/mol) and the enthalpy of activation is rather high (cfl. 145 kj/mol), higher than that is for esterifications ca. 102 kj/mol) [38]. 

SCHEME 6 The amidation and imidation of l-chloro-3-phospholene 1-oxide by reaction with amines. 

SCHEME 14 Phospha-Michael reactions with l-phenyl-2-phospholene 1-oxide. 

Isocyanates have been shown to undergo a high jdeld reaction with carboxylic acids to afford amides. Polymerization of aromatic diisocyanates with aromatic dicarboxylic acids was carried out in the presence of 3-methyl-l-phenyl-2-phospholene 2-oxide to afford aramids (7). The polymerization was carried out in sulfolane at 200 C. Polymers with inherent viscosities of up to 1.8 dL/g were obtained. 

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... 

Definitive evidence on the role of heteroelements in the regjochemical control of the hydrozirconation may be exemplified with the reaction of phospholene-1 (7) with 1. The gem-phosphazirconocene compound 8 is selectively formed with P-coor-dination on the metal fragment. The ]3-zirconated product 10 was prepared with 1... 

Preparation of l-ethoxy-2-phenyl-4,5-dimethoxycarbonyl-A2- 5-phospholene 1-oxide — Reaction of a vinylicphos-phonite diester with an unsaturated carboxylate ester... 

A mixture of diethyl 2-bromo-l-phenylethenylphosphonite (30.3 g, 0.1 mol) and dimethyl maleate (14.4 g, 0.1 mol) was stirred for 4 h at room temperature under an argon atmosphere. At this time, hexane was added to the reaction mixture sufficient for complete precipitation, and the resultant crystals (unreacted dimethyl maleate) were removed by filtration. The oily residue was treated on a silica gel column (40/100 pm) using a pentane/acetone (8 2) mixture, allowing the elution and isolation after evaporation of pure l-ethoxy-2-phenyl-4,5-dimetho x yea rb o n y I - A2-X5-phospholene 1-oxide (8.9 g, 27%), which exhibited spectra and analytical data in accord with the proposed structure. 

Biphilic Reactions.—A most thorough investigation into the cycloaddition of buta-1,3-diene with dichloro(methyl)phosphine (30) has revealed some of the factors which influence the composition of the final products.32 Thus the A3-phospholen 1-oxide (31) is the product of the cycloaddition at room temperature, but at 90 °C the isomeric A2-phospholen 1-oxide (32) predominates after work-up. The yields of (31) and (32) are improved by a new work-up involving methanolysis rather than hydrolysis of the intermediate salts.32... 

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