Allyl phosphine oxides

Addition of Metalated Allylic Phosphine Oxides, Phosphonates, Sulfones, and Sulfoxides and Sulfoximines to a,/i-l nsaturated Carbonyl Compounds... 

Metalated Allylic Phosphine Oxides and Phosphonates Simple Diastcreoselection... 

In contrast to allylic phosphine oxides, phosphonates, sulfones and sulfoxides, the chemistry of lithiated allylic sulfoximines has been less extensively developed25 27. The reaction of lithiated racemic A-phenyl-A -(4-rnethylphenyl)-S -(2-propenyl)sulfoximine with either 2-cy-clopentenone or 2-cyclohexenone gave a complicated mixture with 1,4-oc-ad ducts being slightly favored over the 1,4-7-adducts. The yields of these adducts were poor25. In contrast, lithiated racemic Ar-tert-butyldiphenylsilyl-5-phenyl-5,-(2-propenyl)sulfoximine gives mainly 1,4-y-ad-ducts on reaction with the same enones26. 

Type I (fast homodimerization) Terminal olefins, allylsilanes" Terminal olefins, allylsilanes," 1° allylic alcohols, ethers, and esters, " allyl boronate esters, allyl halides, alkyl-substituted allenes Terminal olefms, allyl boronate esters, 1° allylic alcohols, ethers, and esters,styrenes (no large ortho substit.), " " allyl allylsilanes, allyl sulfides, allyl phosphonates, " allyl phosphine oxides, protected allylamines ... 

Alternatively, the ambident oi-hetero substituted allyl anions have been utilized as homoenolate equivalents. For example, in the presence of HMPA, allyl phenyl sulfides (251),192 allyl phenyl sulfones (252)192b c and allyl phenyl selenides (253)192d e add to a,(3-enones in a l,4(0)-mode, while allyl phenyl sulfoxides (254) and allyl phosphine oxides (255) afford 1 A j-addition exclusively, irrespective of solvent used.193 Hua has shown that additions of either chiral sulfoxide (254 R1 = R2 = R3 = R4 = H, R5 = p-tolyl) or allyl oxazaphospholidine oxide (256) occur with excellent enantioselectivity (>95% ee).194 Similarly, Ahlbrecht reports that the a-azaallyl (257) adds exclusively in a 1 A j-mode to acceptor (59) to afford 1,5-diketones (Scheme 86).195... 

Since allyl sulfoxides may quite easily undergo racemization at the sulfur atom via a reversible [2,3] sigmatropic process, the configurationally more stable chiral allylic phosphine oxides were also investigated.201 Compounds (184) and (185), prepared as a 1 1 mixture from allylphosphonyl dichloride and (-)-ephedrine, were shown to add to cycloalkenones with reasonably high diastereoselectivities. Ozono-lysis of the initially formed 1,4-adducts affords the respective optically active ketoaldehydes (Scheme 67). With a / /-isopropyl-substituted derivative even higher selectivities (88-98% ee) could be obtained. 

S. G. Pyne, Addition of Metalated Allylic Phosphine Oxides, Phosphonates, Sulfones, Sulfoxides and Sulfoximines to a,/3-Unsaturated Carbonyl Compounds , in Stereoselective Synthesis (Houben-Weyl) 4th ed. 1996, (G. Helmchen, R. W. Hoffmann, J. Mulzer, E. Schaumann, Eds.), 1996, Vol. E21 (Workbench Edition), 4, 2068-2086, Georg Thieme Verlag, Stuttgart. 

In analogy to the Peterson alkenation, the intermediate hydroxyphosphine oxidn (269) cm be prepared by addition to epoxide derivatives (268 Scheme 36). Overall yields are high for this process, and this sequence can be applied to the synthesis of phosphonate intermediates as well. Warren has studied hydroxy-directed epoxidation. Provided the allylic phosphine oxide is trisubstituted, as is (270) in equation (6S), these oxidations proceed with good selectivity. Ring opening can then be undertaken to generate the hyth-oxyphosphine oxide. 

It is clear that there is an exception to every rule even in AD there are a few cases known where other ligands gave improved stereoselectivities compared with PHAL, PYR, or IND. Thus, allylic phosphine oxides undergo AD to yield diols which could be used for the synthesis of optically active allylic alcohols [43]. 

The allyl phosphine oxide approach to diene and polyene synthesis has been used by Lythgoe28- in his vitamin D3 synthesis, and by Pattenden29-1 in syntheses of compounds such as 31. 

The main classes of allyl phosphine oxide which cannot be used in diene syntheses, as they react in the 7-position30, are those with an aryl group in the a-posi-tion 32, or with a four 33 or five 34 membered ring. Those with just one a-sub-stituent and no 0- or 7-substituents 35 also give some 7-adduct31. ... 

The carbonyl adducts of allyl phosphine oxides, e. g., 24 and 29 can also be used to make allyl alcohols32 by the reductive removal of the Ph2PO group with lithium aluminium hydride a reaction involving transposition of the double bond, e. g., 24 36. In this approach, the allyl anion of 23 is a reagent for the vinyl anion synthon 37. 

Epoxides of Allyl Phosphine Oxides as Allyl Cation Equivalents... 

Sulphenylation of allyl phosphine oxide anions gives only 7-addition, in contrast to the predominantly a attack with other electrophiles (Sect. 2.1). This is because the product of a attack can isomerise by a [1,3] shift22. The product of the reaction is a mixture of allyl isomers 156 and 157. These both give the anion 158 on treat-... 

The sulfone 98 allows a tandem (chapter 36) sequence of remarkable selectivity. The lithium derivative of the allylic phosphine oxide 96 (see chapter 12) adds to the enone 97 to give the lithium enolate 99 trapped by the sulfone 98 to give the complex product 100 in 96% yield the only imperfection in stereochemical control is 3% of the Z-vinyl phosphine oxide.16... 

The specific preparation of either phosphine oxide 73 or 80 can easily be carried out from the appropriate allylic alcohol. The reaction is like the one we saw for the preparation of allylic alcohols from allylic sulfoxides but the [2,3]-sigmatropic rearrangements 76 and 78 run only in this direction with phosphorus.11 It is also the preferred direction with sulfur. Since allylic alcohols 75 and 78 are stable to the allylic rearrangement, each alcohol gives specifically one allylic phosphine oxide 73 or 80 or allylic sulfoxide 41 or 77. This is the theme for most of the rest of the chapter. 

Scheme 5.39. Allyl sulfoxide additions , fa 1,4-mechanism [198]. (b) Tandem 1,2-addition / 3,3-rearrangement mechanism [148] (see also ref. [199]). (c,d) Transition structures for allyl phosphine oxides [196,197]. Inset Gauche pentane interaction between lithium and the N/je methyl.

Bis(acetonitrile)dichloropalladiuin(ll). 14, 35-36 15, 28-29 16, 25-26 17, 30-31 Allylic rearrangement. This suprafacial rearrangement finds use in the preparation of 4-acetoxy-2-alkenonitriles and 6-hydroxy allylic phosphine oxides. ... 

Homoallyic amines. Isoxazolines derived from allylic phosphine oxides can be converted by nickel boride to the saturated 1,3-amino alcohols. On further reaction, elimination of phosphinic acid occurs. 

Allylic phosphine oxides Wittig-Homer synthesis of 1,3-dienes Allylic phosphine oxides can be prepared by reaction of 2,6-dichlorobenzoates of allylic alcohols with lithium diphenylphosphide followed by oxidation. Thus... 

Allylic alcohols, 1, 17, 28-29, 30-31, 85-86, 182, 261, 318, 335, 338, 425, 444, 588, 602-603, 604, 664 AUyUc amines, 604-605 Allyhc chlorides, 598, 645 Aiiylic dibromides, 418 AUylic ethers, 269 Allylic halides, 327, 329 Allyhc hydroperoxides, 287 Allylic phosphine oxides, 340 Allylic rearrangement, 11-12 Allylic trifluoroacetoxylation, 360-361 Allylidenetriphenylphosphorane, 14-15 a-Allylpalladium chloride complexes, 45-47... 

Chiral allylic phosphine oxides were synthesized by the rhodium-catalyzed asymmetric hydroalkoxylation of diphenylhosphinylallenes (Scheme 37). Using thiophenols, hydrosulfenylation reactions were carried out." ... 

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