Regiospecificity styrene/olefins

Regiospecific cycloaddition of 65 a, b, and c to furan has also been observed. None of the oxazolinones give photoadducts with other olefins, including methyl vinyl ether, cyclohexene, cis-2-butene, trans-2-butene, and styrene. 

For triethylaluminum, the two-step synthesis [Eqs. (a) and (b)] is essential it is also recommended for tripropylaluminum and should be used if pure R3AI compounds are required Reactions (a) and (b) are regiospecific for terminal olefins, leading almost exclusively to the n-alkyls. However, with styrene or with trialkylvinylsilane, mixtures are observed (see also 5.3.3.4.1). The reaction of Al, H2 and trimethylvinylsilane gives the RAIR 2 compound in low yield ... 

The various methods of generating o-quinone methides,4-5 including the thermal or (Lewis) acid-catalyzed elimination of a phenol Mannich base,149 150-160-161163 the thermal or (Lewis) acid-catalyzed dehydration of an o-hydroxybenzyl alcohol (ether),147-149-151-153-156-157-162-163-165-168 171-175-178-183 the thermal 1,5-hydride shift of an o-hydroxy styrene,171-173 175 178-183 the thermal dissociation of the corresponding spirochromane dimer,158 163-164,166 oxidation of substituted o-alkylphenols,152-170 and the thermal or photochemical-promoted cheletropic extrusion154-155 159 of carbon monoxide, carbon dioxide, or sulfur dioxide (Scheme 7-III), as well as their subsequent in situ participation in regiospecific, intermolecular [4 + 2] cycloadditions with simple olefins and acetylenes,147 149-151 152 153159 162-164... 

The reaction of nitrone 101 with such olefins 5 as propylene, n-hexene, allyl alcohol, styrene, acrylic acid, methyl acrylate, acrylonitrile, and butadiene are all regiospecific to give S-substituted isoxazolidines of type l.77 The reaction with olefins 6 seems to be regio- and stereo-specific thus, nitrone 101 and methyl methacrylate give cycloadduct lilt as the sole product.77 Similarly, 101 and 1 -methyl-1-phenylethylene gives adduct Hit.77 In the reactions with olefins 7 or 8, the stereospecificity is more evident.77,78 The isoxazolidine obtained is always one of the two possible epimers. The reaction of nitrone 101 with trisubstituted olefins is highly stereoselective.64 Some results are summarized in Table III. 

Insertion of aromatic olefins (styrene and/or homologues thereof) was studied not only with the aforementioned N N-modified catalytic systems (N N is 2,2 -bipyildine or 1,10-phenanthroline) but also with [ (5)-Bz-DBHOSOX Pd(COCH3)(Solvent)](OTf), where (,5)-Bz-DBPHOSOX is (5)-2-[2-(5 /-benzo[fc]phosphinindol-5-yl)phenyl]-4-benzyl-4,5-dihydrooxazole (Scheme The insertion was regiospecific, both with... 

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