Allyl cations, 2-methyl cycloaddition reactions

A review of intramolecular 4 + 3-cycloadditions of allyl cations has been presented.277 The 4 + 3-cycloaddition reaction of C(2)-substituted furans with 1,3-dimethyloxyallyl cations show high endo diastereoselectivity and a cis dia-stereospecificity.278 The tandem Peterson olefination/[4 + 3]-cycloaddition of tertiary alcohols (149) in the presence of filran and Lewis acids (TiCLt) furnishes cycloheptanes (150) in modest yields (Scheme 57).279 (Trimethylsilyl)methyl allylic sulfones (151) were used to investigate the scope and limitations of intramolecular 4 + 3-cycloadditions of allylic sulfones (Scheme 58).280 Lewis acid-catalysed 4 + 3-... 

Stereoselective Diels-Alder reactions have been reported in several cases. Enantioselective Diels-Alder reactions of l-phenoxycarbonyl-l,2-dihydropyridine with 1-alkylated acryloyl-pyrazolidin-3-ones using a chiral cationic palla-dium-phophinooxazolidine catalyst afforded chiral isoquinuclidines with excellent enantioselectivity <2005TL5677>. Bismuth(lll) chloride-mediated diasteroselective intramolecular [4-f2] cycloaddition reactions of A-allyl derivatives of pyrazole aldehydes led to fused sulfur-containing pyrazole heterocycles <2003SC3063>. A highly diastereoselective intramolecular hetero-Diels-Alder approach toward tetracyclic pyrazoles from 5-(3-methyl-2-butenylthio)-3-methyl-l-phenyl-4-pyrazolecarboxaldehyde has been reported <1997SL1155>. 

X = Y = CO M = Mo, X = CO, Y=T] -allyl), the K -N,N,N coordination pattern has been observed. The complexes [M(Tm )Me] (M = Zn, Cd, Hg) have been recently reported and investigated for their ability to exchange alkyl and sulfur donor hgands between the Group 12 metals. A number of cationic Pt(IV) carbene complexes [Pt(=C(OMe)(NHR)) (Tp )(Me)2] (OTf) have been synthesized (R=Et, Pr, Pr, Bn OTf=trifluoromethanesulfonate) by methylation with MeOTf of the Pt-carboxamido precursors [Pt(C(=0)(NHR))(Tp )(Me)2]. A computational study on the mechanism of trimerization of aUcynes in the presence of a hydrotris(pyrazolyl)borate iridium catalyst [lr(Tp)(Ti -HC=CH)2] and the effect of substituent groups in R-C=C-R (R = Me or OCOMe) has been reported, demonstrating that two mechanisms for the formation of the benzene complex, including the intramolecular [4 + 2] cycloaddition and Schore mechanisms, are possible in this reaction. 

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