Acyl-allyl

In the Pd-catalyzed cross-coupling reactions of acylzirconocene chlorides with allylic halides and/or acetates (Section 5.4.4.4), the isolation of the expected p,y-unsaturated ketone is hampered by the formation of the a, P-un saturated ketone, which arises from isomerization of the p,y-double bond. This undesirable formation of the unsaturated ketone can be avoided by the use of a Cu(I) catalyst instead of a Pd catalyst [35], Most Cu(I) salts, with the exception of CuBr - SMe2, can be used as efficient catalysts Thus the reactions of acylzirconocene chlorides with allyl compounds (Table 5 8 and Scheme 5 30) or propargyl halides (Table 5.9) in the presence of a catalytic amount (10 mol%) of Cu(I) in DMF or THF are completed within 1 h at 0°C to give ffie acyl--allyl or acyl-allenyl coupled products, respectively, in good yields. ill... 

Keywords Acetals, Acylals, Allylations, Bismuth(III), 3,4-Dihydro-2//-l -benzopyrans, Ene reactions, Epoxide-olefin cyclizations, Piperidines, Tetrahydro-quinolines, THP ethers... 

Ring contraction of cyclopentenone and cyclohexenone derivatives to cyclobutanes was observed during direct irradiation of various j5,y-unsaturated cyclohexenones. By way of a Nor-rish type I cleavage in n,7i excited singlet (5t) and n,7t excited triplet (T2) states, an acyl/allyl diradical is formed which recombines in the allyl position to form the product of a 1,3-acyl migration,102 while sensitized irradiation leads mainly to oxa-di-rr-methane rearrangement (see Section 4.2.3.). 

Hammaecher, C. and Portella, C. (2008) New 6-oxa-2-silabicyclo[2.2.0]hexanes by photochemical conversion of acyl(allyl) (dimethyl)silanes. Chemical Communications, 5833—5835. 

Note that the multiple bond of unsaturated o-organyls (e.g. alkenyls, alkynyls, acyls, allyls) may present an alternative site to the M-C bond for electrophilic attack. 

Allylic Oxidation. The Kharasch-Sosnovsky reaction involves oxidation of the allylic position while the olefin remains intact. In the presence of catalytic copper (II) salts, treatment of olefins with peresters affords acylated allylic alcohols. When (S)-(—)-4-(2-methylpropyl)-2-(2-pyridyl)-2-oxazoline was involved, (R)-cyclohexenyl benzoate was isolated in 57% yield and 28% ee (eq 6). ... 

Phosphorus Containing Ring Systems. 1-Acyl allyl phosphonates (376) exposed to the action of m-CPBA in the presence of MgS04 are readily cyclized... 

R= acyl, allyl, aryl, vinyl, benzyl R = aryl, vinyl... 

Carbostannation of alkynes, and 1,2- and 1,3-dienes can be brought about by acyl, allyl, or alkynyl-stannanes in the presence of a nickel(O) catalyst. ... 

The scope of the Negishi reaction is broad, similar to that of Stille and Suzuki cross-coupling. The reaction seems to work if R = aryl, vinyl, alkynyl, acyl, allyl, benzyl, homoallyl (-CH2-CH2-CH=CH2) and homobenzyl (-CH2-CH2-Ph), or even primary alkyl, and if X = I, Br, or OTf (Cl works, but often sluggishly). Correspondingly, R = aryl, vinyl, alkynyl, allyl, benzyl, and primary alkyl. The organozinc reagent may either be used as a preformed compound, such as R2Zn... 

Ruthenium-catalyzed hydroacylation of 1,3-dienes with aromatic and heteroaromatic aldehydes occurs in relatively good yields to afford the corresponding fi, /-unsaturated ketones . Isoprene and benzaldehyde were treated with 4 mol% Ru(COD)(COT) (COD = 1,5-cyclooctadiene, COT = 1,3,5-cyclooctatriene) and 4 mol% PPhs under argon for 40 hours to give 54% 80 (equation 41). The key intermediate is an acyl- ) -(allyl)ruthenium complex which undergoes reductive elimination to give the corresponding... 

We have considered a variety of related intermediates in this chapter as extended versions of enolate ions 191 and as dienes. Another legitimate way to consider them is as acylated allyl anions 191c, and this leads us to the next chapter where we consider how to use allyl anions in synthesis. 

The sequential trans-addition of a carbon nucleophile and a carbon electrophile across an arene double bond in (arene)Cr(CO)3 was first reported in 1983 [35]. Since then this methodology has undergone extensive development, with recent efforts mainly directed towards enantioenriched products [36]. Anionic (cy-clohexadienyl)Cr(CO)3 complexes are very soft nucleophiles and this places restrictions on the electrophiles that can be used in this sequence. Specifically these reactions are successful when carbanion dissociation from the intermediate anionic cyclohexadienyl complex is slow compared to the reaction with the carbon electrophile. The sequential addition is usually carried out as a one-pot reaction and the proposed reaction sequence is that shown in Scheme 11. In contrast to the nucleophile addition/protonation sequence, products form with excellent 1,2-regioselectivity. It is likely that this is due to an irreversible transfer of the acyl, allyl, or propargyl group to one of the two termini of the cyclohexadienyl ligand. 

Examples of the aza-Claisen rearrangement of allyl vinyl amines and the thia-Claisen rearrangement of allyl vinyl sulfides have been reported. An efficient Lewis acid-catalysed Claisen rearrangement of zwitterionic A-acyl allylic amines... 

Scheme 19.3 Dynamic kinetic resolution of an O-acylated allylic alcohol based on palladium-catalyzed racemization and enzymatic ester hydrolysis.

The mass of this work lies beyond the scope of this review, but a few prominent points may be cited. In most cases, treatment of either an alkyl or an acyl tetracarbonyl cobalt complex with triphenylphosphine gives only the acyl derivative, [Co(COR)(CO)3P(C6H5)3] (304, 306). The reactions of acyl, allyl, and hydridocobalt tetracarbonyl or acetylenedicobalt hexa-carbonyl complexes with phosphines are first order in the cobalt complex, so a dissociation mechanism prevails (64, 65, 66). However, the reaction between [Co(CO)3NO] and P(C6H5)3 is second order (66). 

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