Allyl phosphite rearrangements

Allyl phosphite rearrangements, 138-142 Aluminum-phosphorus cubane, 60-61 Aluminum tris(methyl methylphosphonate),... 

The allyl sulfoxide-allyl sulfenate rearrangement can be used to prepare allylic alcohols.275 The reaction is carried out in the presence of a reagent, such as phenylthi-olate or trimethyl phosphite, that reacts with the sulfenate to cleave the S—O bond. 

An allylic phosphorus ester rearrangement to form a new C-P bond has been reported under photochemical conditions.179 Under irradiation in the presence of 9,10-dicyanoanthracene, an allylic phosphite ester undergoes rearrangement to form the corresponding allyl-icphosphonite ester (Equation 4.40). Benzophenone serves only poorly as a photosensitizer in this reaction. 

One of the photorearrangements studied in this laboratory is the conversion of allyl phosphites to the the corresponding phosphonates (74). Although this rearrangement occurs thermally at 2(X) (72), the photochemical process proceeds readily at room... 

When the deuterium-labeled allyl phosphite of Scheme V was irradiated directly in cyclohexane with 254 nm light, the deuterium in the phosphite was nearly totally scrambled indicating that the singlet state rearrangement involves a combination of what are formally 1,2- and 2,3-sigmatropic shifts. The phosphite did... 

Janecki, T, and Bodalski, R., A convenient method for the synthesis of substituted 2-methoxycarbonyl-and 2-cyanoallylphosphonates. The allyl phosphite-allyl phosphonate rearrangement, Synthesis, 799, 1990. 

A new approach to diethyl 2-methoxycarbonyl-2-alkenylphosphonates is based on the thermally indnced Michaelis-Arbnzov rearrangement of diethyl allyl phosphites withont added alkyl halide (Scheme 8.39). The procednre involves treatment of the readily accessible allyl alcohols with diethyl chlorophosphite followed by heating of the crude intermediates for several hours at 7O-IOO"C. The presence of a methoxycarbonyl group facilitates the rearrangement, the optimum temperatures being lower than those reported for unfunctionalized analogues. 

The use of NiCl2 catalysts in the rearrangement of allylic phosphites (and related compounds) to allylic phosphonic (or phosphinic) acids has already been reported (Organophosphorus Chemistry, 1988, 1, 144), and the same authors have now described the use of Ni(cyclooctadiene) catalysts in the presence of bistrimethylsilylacetamide in the reactions between allylic esters,or carbonates, and dialkyl phosphites, monoalkyl alkylphosphonates,or monoalkyl... 

Diallylsulfonium salts undergo intramolecular allylic rearrangement with strong bases to yield 1,5-dienes after reductive desulfurization. The straight-chain 1,5-dienes may be obtained by double sulfur extrusion with concomitant allylic rearrangements from diallyl disulfides. The first step is achieved with phosphines or phosphites, the second with benzyne. This procedure is especially suitable for the synthesis of acid sensitive olefins and has been used in oligoisoprene synthesis (G.M. Blackburn, 1969). 

Carboxylic acids react with butadiene as alkali metal carboxylates. A mixture of isomeric 1- and 3-acetoxyoctadienes (39 and 40) is formed by the reaction of acetic acid[13]. The reaction is very slow in acetic acid alone. It is accelerated by forming acetate by the addition of a base[40]. Addition of an equal amount of triethylamine achieved complete conversion at 80 C after 2 h. AcONa or AcOK also can be used as a base. Trimethylolpropane phosphite (TMPP) completely eliminates the formation of 1,3,7-octatriene, and the acetoxyocta-dienes 39 and 40 are obtained in 81% and 9% yields by using N.N.N M -tetramethyl-l,3-diaminobutane at 50 in a 2 h reaction. These two isomers undergo Pd-catalyzed allylic rearrangement with each other. 

The photo-Arbuzov rearrangement of allyl-, benzyl- and naphtylmethyl-phosphites (Scheme 13), first developed by Bentrude et al. [20], found applications in the preparation of phosphonates (70-90%) [38]. Arylphosphonates have been shown to act as protein tyrosine kinase inhibitors [39] or non-hy-drolyzable analogs of phosphorylated tyrosine residues [40]. 

Although the interception of allylic sulfenates in the manner described by equation 11 was first observed by Abbott and Stirling ", the general value of this transformation and its remarkable synthetic potential has been recognized by Evans and coworkers , who have also introduced the previously used trimethyl phosphite as a preferable trapping agent. An early review of the synthetic utility of the reversible allylic sulfoxide-sulfenate rearrangement has also been published by Evans and Andrews . 

If the insertion step following oxidative addition occurs on one of the two fragments resulting from oxidative addition, an intramolecular catalytic reaction (C—O — C—C rearrangement) takes place (example 40, Table III). It is interesting to note that two different products—2,6- and 3,6-heptadienoic acids—can be obtained from allyl 3-butenoate. Their ratio can be controlled by adding 1 mole of the appropriate phosphine or phosphite to bis(cyclooctadiene)nickel or similar complex. Bulky ligands favor the 2,6 isomer. It is thus possible to drive the reaction toward two different types of H elimination, namely, from the a or y carbon atoms. 

The cycloaddition of allenyl sulfoxide 135 and cydopentadiene occurred at room temperature, giving the single adduct 136. The initially formed allylic sulfoxide underwent a rapid [2,3]-sigmatropic rearrangement. Treatment of 136 with trimethyl phosphite furnished alcohol 137. It should be noted that the reaction of methyl 4-hydroxy-2-butynoate with cydopentadiene failed to give 137. Thus, the allene 135 is considered as a masked and more reactive alkyne equivalent. 

One notable advance in this chemistry since the publication of CHEC-II(1996) is the use of enantiomerically enriched 3,6-dihydro-l,2-thiazine 1-oxides in the rearrangement sequence. For instance, iV-Cbz-protected bicyclic 1,2-dihydrothiazine 44 undergoes ring opening upon treatment with phenylmagnesium bromide (Scheme 16). The synthesis of allylic amino alcohol 129 is completed in excellent yield upon exposure of the intermediate sulfoxide 130 to trimethyl phosphite and methanol at 80 °C <2002TA2407, 2000TL3743>. 

Another [2,3] sigmatropic rearrangement converts allylic sulfoxides to allylically rearranged alcohols by treatment with a thiophilic reagent such as trimethyl phosphite.539 In this... 

Allyl sulfoxide -> sulfenate rearrangement.2 A key step in a stereoselective first synthesis of withaferin A (3), a steroid antitumor agent, is the production of the desired A/B ring system by an allyl sulfoxide-> sulfenate rearrangement in the presence of trimethyl phosphite (equation I). 

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. 

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