Phospholenic compounds

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. 

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... 

Two series of phosphoranes (86 or 87) containing a dioxaphos-pholene ring and a 2-phospholene or 3-phospholene ring have been synthesised from trico-ordinate phospholenes (83) or (84) and 1,2-dicarbonyl compounds (85)1 7. The compounds were characterised by analysis, XH and J1P n.m.r. and, in contrast to earlier work,1 8 were found to be stable towards the retrodiene fragmentation. 

Treatment of phosphorus trichloride with isoprene in the presence of acetone leads to 1-chlorophospholen 1-oxides (33).33 Evidence has been presented that the diene reacts first with the trichloride to produce (34), which then reacts with acetone.33 l-Bromo-3,4-dimethyl-A3-phospholen (35) does not form a spiro-compound with 2,3-dimethylbuta-l,3-diene, although the bisphospholen derivative (36) has been isolated after hydrolytic work-up.34... 

Going one stage further phospholes present distinctive features on account of the aromatic character <1967 78 1969,77) this property is clearly reflected in the values of the coupling constants. The relevant data for 1-methyl phospholes have been published (1969>77) and are shown in 98 these are obviously contrary to the trends previously reported for 2-phospholenes in which 2/(P-CH) < 3/(PCCH). However, these are in agreement with observations on l-phenyl-2,5-dimethylphosphole (99)(1967 70) and on l-phenyl-3,4-dimethylphosphole (100) (1969,20) in the latter compound both couplings mentioned have been found to be of the same sign. 

A reversal of the McCormack synthesis was observed when c s,m-2,5-dimethyl-3-phospholene was treated with diethyl peroxide. The intermediate phosphorus compound (P-C/V = 5) decomposes spontaneously to trans,trans-1,4-hexadiene (equation 46)... 

Structure determination of phospholenes (P-C/V = 3) is often complicated since these compounds are air sensitive and not easy to handle. The situation is much better with phospholenes with P-C/V = 4, as exemplified by l-phenoxy-l-oxo-3- and -2-phospholenes (81) and (82) which have recently been studied (81PS(9)293>. Each of the two isomers can be prepared in high yield as a crystalline compound from the corresponding 1-chloro-1-oxophospholene. 

Keywords Phospha sugar Phosphorus heterocycle P - C compound Phospholene Phospholane... 

The 3-phospholene 1-oxide derivative is a potential heterocycle for easily producing chemically modified phosphorus heterocycles because the compound possesses a reactive C=C double bond, allylic methylene, an electron-deficient methylene group a-positioned to phosphorus, etc. 4-Chloro-l,6-dihydrophosphinie derivatives 16A and 16B are prepared from dichloro-carbene adducts 15 with l-(R)-3-ethylphospholene 1-oxide (Scheme 5) [4]. 

A great number of dihydrophospholes, namely 2- and 3-phospholenes, and tetrahydrophospholes (phospholanes) are known. These compounds have found significant utility as building blocks for the preparation of chiral ligands. 

Interest has also continued in phosphinidene (RP ) chemistry. Evidence from mass spectrometry has led to the conclusion that phenylphosphinidene, PhP , is a stable species in the gas phase.The existence of p-phenylenebi-sphosphinidene (332) has been considered from a theoretical standpoint. " The reactivity of coordinated phosphinidenes has received further study. The first examples of genuine 1,4-additions of the complex PhP=W(CO)5 with 1,3-dienes, giving phospholene complexes, e.g. (333), have been reported. " " Phosphiranes are formed as intermediate species in the reactions of complexed phosphinidenes with chloro-alkenes, which lead ultimately to vinylphosphorus compounds (334), essentially insertion products of the phosphinidene into the... 

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. ... 

In this chapter, we attempt to review the current state of the art in the applications of cinchona alkaloids and their derivatives as chiral organocatalysts in these research fields. In the first section, the results obtained using the cinchona-catalyzed desymmetrization of different types of weso-compounds, such as weso-cyclic anhydrides, meso-diols, meso-endoperoxides, weso-phospholene derivatives, and prochiral ketones, as depicted in Scheme 11.1, are reviewed. Then, the cinchona-catalyzed (dynamic) kinetic resolution of racemic anhydrides, azlactones and sulfinyl chlorides affording enantioenriched a-hydroxy esters, and N-protected a-amino esters and sulftnates, respectively, is discussed (Schemes 11.2 and 11.3). 

Phospholans and Phospholens.—Details have appeared of the preparation and properties of homocubylphosphoranes, e.g. (24), and related compounds. An improved synthesis of (24) is as shown. A full account has been given of the dynamic n.m.r. of the spirophosphoranes (25) in which the naphthyl... 

PhosphoIene sulphides (IS) and oxides have been prepared by [1+4] cycloaddition reactions of (14) with various dienes. Phosphorus analogues (17) and (19) of erythrofuranose have been prepared by stereospecific ci.y-hydroxylation of the 2-phospholene-l-oxides (16) and (18), respectively.Compounds (17) and (19) readily epimerise at C-2 on treatment with base. 

Aromatic isocyanates, particularly those containing electron-attracting substituents, react noticeably more easily than aliphatic isocyanates. In the former case it often suffices to leave the components for some hours at room temperature in a water-pump vacuum, whereas for aliphatic compounds boiling under reflux is usually necessary and sometimes use of a higher-boiling solvent such as decalin. The best catalysts are cyclic phosphine oxides of type (1) (phospholene oxides)862 and cyclic phosphonic diamides of type (2) (1,3,2-diazaphospholidine oxides).863 The best results were obtained with compound (1, R = C2H5) (for its preparation see Campbell et a/.862) the phenyl compound, although more readily prepared,864 is somewhat less reactive. The amounts of catalyst needed are 0.1% for (1) or 0.5% for (2). 

Since the double-bond isomerization was at first unrecognized and later recognized only in the hydrolysis products, the position of the double bond in most of the compounds described in the literature must be regarded as uncertain. The only proved facts seem to be that with isoprene dichloro(phenyl)-phosphine gives the 2-phospholene derivative, that dichloro(methyl)phosphine and dibromo(phenyl)phosphine give the 3-phospholene, whereas also with 2,3-dimethylbutadiene dichloro(phenyl)phosphine gives the non-isomerized product of type (1).38,39... 

The addition occurs in the presence of polymerization inhibitors such as copper stearate, aromatic polynitro compounds, or sterically hindered phenols and then sometimes requires days or weeks. In spite of the often tedious procedure the method is of great interest since, from cheap materials, it often affords good yields of compounds containing the phospholene ring system which is otherwise difficultly accessible. Compounds of type (1) and (2) have also considerable interest as efficient catalysts for the carbodiimide synthesis (cf. page 504). 

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