1.3- Cyclohexadiene, singlet oxygen cycloaddition

Isopropyl-l, 3-cyclohexadiene, singlet oxygen cycloaddition, 262-3 Isopropyl ether, hydrotrioxide formation, 740 7-Isopropylidenenorbomenes,... 

Cycloadditions of singlet oxygen to particular fused 1,3-cyclohexadienes can be highly diastereoselective, and therefore useful in the total syntheses of some complex natural products. For example, chemically generated 02 effectively and stereoselectively adds to the termini of the 1,3-diene system in 515 to give a single endoperoxide 516 (81%),... 

Cyclohexadiene and singlet oxygen form (103). Most of the important synthetic approaches for 1,2-thiazines use a fragment in which the S-N bond already exists. Syntheses via [4 + 2] cycloadditions constitute a major part of the synthetic repertoire for this class of compounds (CHEC-II(6)370). Thus, pentadiene with TsNSO gives (104) and perfluoro-l,2-thiazine (105) is prepared by the cycloaddition of thiazyl fluoride (FSN) and perfluoro-1,3-butadiene CF2 = CFCF = CF2 (79CC35). 

Salamci, E., Secen, H., Siitbeyaz, Y. and Bald, M. (1997) A condse and convenient synthesis of dl-proto-quercitol and dl-golo-quercitol via ene reaction of singlet oxygen combined with [2 + 4] cycloaddition to cyclohexadiene. Journal of Organic Chemistry, 62 (8), 2453-2457. 

Salamci, E., Secen, H., Sutbeyaz, Y., Balci, M., A Concise and Convenient Synthesis of dl proto Quercitol and dl gala Quercitol via Ene Reaction of Singlet Oxygen Combined with [2 + 4] Cycloaddition to Cyclohexadiene, J. Org. Chem. 1997, 62, 2453 2457. 

One of the most reactive substrates for endoperoxide formation is 1,3-cyclopentadiene. Rate constants of 1 X 10 (in chloroform) and 3.9 x 10 (in toluene) mol seer have been determined. The kinetics and the solvent dependence of the singlet oxygen [4 -i- 2]-cycloaddition with 1,3-cyclohexadiene have been investigated in detail. - The rate constant decreases about tenfold when the ring size is increased by one methylene unit (Table 25.1). 

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