1.4- dichloro-2-butene cycloaddition

The final series of five procedures presents optimized preparations of a variety of useful organic compounds. The first procedure in this group describes the preparation of 3-BROMO-2(H)-PYRAN-2-ONE, a heterodiene useful for (4+2] cycloaddition reactions. An optimized large scale preparation of 1,3,5-CYCLOOCTATRIENE, another diene useful for [4+2] cycloaddition, is detailed from the readily available 1,5-cyclooctadiene. Previously, the availability of this material has depended on the commercial availability of cyclooctatetraene at reasonable cost. A simple large scale procedure for the preparation of 3-PYRROLINE is then presented via initial alkylation of hexamethylenetetramine with (Z)-1,4-dichloro-2-butene. This material serves as an intermediate for the preparation of 2,5-disubstituted pyrroles and pyrrolidines via heteroatom-directed metalation and alkylation of suitable derivatives. The preparation of extremely acid- and base-sensitive materials by use of the retro Diels-Alder reaction is illustrated in the preparation of 2-CYCLOHEXENE-1.4-DIONE, a useful reactive dienophile and substrate for photochemical [2+2] cycloadditions. Functionalized ferrocene derivatives... 

Cl2Si=CHCH2/Bu is easily synthesized by the reaction of trichlorovinylsilane with rbutyllithium in nonpolar solvents [2-4] and reacts in a [2+2] cycloaddition reaction with disubstituted alkynes to give 1,1 -dichloro-2,3-diorganyl-4-neopentyl-l-silacyclo-2-butenes [5]. 

The thiirane-forming cycloaddition follows a stereospecific path. This reaction has been shown for three pairs of olefins (2,3), cis-frarw-butene-2, cw-frflfw-l,2-dichloro- and difluoroethylenes. 

Cu(OTf)2-bis(oxazolinyl)carbazole promoted the 1,3-dipolar cycloaddition reaction between CdV-diphenylnitrone and acyloyloxazolidinone with 100% regioselectivity. A key step in the 5-step synthesis of (25,3 S, 4/ )-4-hydroxyisoleucine was the 1,3-dipolar cycloaddition reaction of a chiral nitrone derived from (-)-menthone to ( )-1,4-dichloro-2-butene. ... 

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