Cyclic allyl phosphites

Allyl)CpFe(CO)(PR3) complexes (14) have been prepared from the dicarbonyls, by photolysis in the presence of phosphine or phosphite. The substitution is often aided by a trace of (CpFe(CO)2)2, which is indicative of a radical (see Radicals) chain substitution mechanism. Phosphite ligand (as in 15) has been reported as being a particularly good replacement ligand from the standpoint of thermal stability.Nevertheless, neither C-3-substituted ()] -allyl)Fp complexes (14b) nor cyclic allyl complexes (see Allyl Complexes) may be made directly by this method the carbocyclic cases have been prepared by methoxide-induced proton abstraction of aUcene cation (16) (Section 4.3.2). " ... 

Cyclization of butadiene catalysed by Ni(0) catalysts proceeds via 7r-allylnickel complexes. At first, the metallacyclic bis-7i-allylnickel complex 6, in which Ni is bivalent, is formed by oxidative cyclization. The bis-7r-allyl complex 6 may also be represented by cr-allyl structures 7, 8 and 9. Reductive elimination of 7, 8 and 9 produces the cyclic dimers 1, 2 and 3 by [2+2], [2+4] and [4+4] cycloadditions. Selectivity for 1, 2 and 3 is controlled by phosphine ligands. The catalyst made of a 1 1 ratio of Ni and a phosphine ligand affords the cyclic dimers 1, 2 and 3. In particular, 1 and 3 are obtained selectively by using the bulky phosphite 11. 1,2-Divinylcyclobutane (1) can be isolated only at a low temperature, because it undergoes facile Cope rearrangement to form 1,5-COD on warming. Use of tricyclohexylpho-sphine produces 4-vinylcyclohexene (2) with high selectivity. 

Miscellaneous.- A simple method to resolve racemic l,l -binaphthalene-2,2 -diol involves reaction with menthyl phosphorodichloridite (139) and separation of the diastereomeric phosphites by crystallisation from ether. The new cyclic chlorodiaminophosphine (140), prepared in and two new cyclic triaminophosphines (141) have been used to determine the enantiomeric purity of chiral alcohols, thiols, and amines by means of Ip n.m.r. New optically pure phosphites used for Rh catalysed asymmetric hydroformylation reactions are (142), two diastereomers of (143), and (144) the diphosphinite (145) was similarly employed. Some new cyclic aminophosphines (146) were prepared for use as ligands in asymmetric Pd catalysed allylic substitution reactions. 

When cyclic phosphites were treated with allyl bromide (42b), in the presence of TBAF, a-arylphosphonates were regjoselectively obtained. However, the more reactive thiophosphite (41b) gave the double phos-phonylation product under these conditions in a single step. 

Mechanistically, hydrophosphonylation and hydrothiophosphonylation takes place via pentacoordinate state that could be achieved only toward fluoride ion activation F in ionic liquid medium. Other anions, e.g. Cl , Br , I or HP04 did not work because they are not strong enough to lead to hypervalency. If other sterically hindered and less reactive cyclic phosphites (47a) and (47b) were treated with equimolar quantity of TBAF, the P-F bonded intermediate (48a) or (48b) was formed as confirmed by NMR analysis. These intermediates were then reacted with allyl bromide H2C = C(C02Me)CH2Br, to give phosphonate (49) as a sole product (Figure 4). 

Swamy has reported a simple transition metal-free hydro/hydrothiophos-phonylation of MBH adducts, substituted allyl bromides, allenylphosphonates and alkynes, promoted by fluoride ion in an ionic liquid (Scheme 3.212). It was the first time that clear-cut evidence was provided for fluoride activation of the phosphite via pentacoordinate phosphorus. The reaction of cyclic phosphites 476 with various MBH adducts 477 in the presence of (n-Bu)4N F (TBAF) in [bmimj pFg] leads selectively to y-hydroxyphosphonates 479. In contrast, the corresponding reaction of 476a with MBH acetates affords P-CH2 allylphosphonates 481 with the elimination of acetic acid, " and the... 

In an old patent, Friedman prepared homopolymers from cyclic phosphites and phosphonates with allyl functions (Scheme 3.12). These compounds were homopolymerized or copolymerized with other monomers such as styrene or acrylate monomers in the presence of conventional initiators or from UV activation. The polymers produced quite tough, hard, colorless and clear non-burning plastics. 

Scheme 3.12 Structures of allyl monomers containing cyclic phosphite or phosphonate.

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