1.3- Dienes regioselectivity

Similar conversions were reported with 1,2,3,4,5-pentamethylcyclopenta-l,3-diene, to give stereoselectively the ent/o-6-phenyl-e.vo-4-methyl isomer of pentamethylphenylbicy-clo[3.1.0]hex-2-ene with > 85% yield.Benzylidene transfer to (Z)- and ( )-penta-l,3-diene, isoprene and 2-chlorobuta-l,3-diene regioselectively occurred at the more electron-rich C-C double bond to give trans- and cw-phenylvinylcyclopropanes. The transjcis ratio ranged from 0.52 to 2.2. 

Chevalier, E. Al-Badri, H.. and Collignon, N., Reactivity of substituted 3-(diethylphosphonyl)-l-(trialkylsilyl)alka-l,3-dienes. Regioselective epoxidation and cyclopropanation reactions. Heteroatom Chem., 10, 231, 1999. 

Aza-di-n-methane (ADPM)- rearrangement reactions of both 1-aza- and 2-aza-1,4-dienes are known but not so common at the present time. Nevertheless, and largely due to the work of Armesto et a/., the potential utility of such processes is becoming clearer. In the case of ADPM rearrangement reactions involving 1-aza-1,4-dienes, regioselective conversions are observed with, for exanple, the oxime 23 being converted into cyclopropane 24 in 74% yield after irradiation under triplet-sensitized conditions for just 30 min fScheme 9.S1. 

Keywords Electron-deficient arenes, unactivated 1,3-dienes, bismuth triflate, nitromethane, room temperature, intramolecular double hydroarylation of 1,3-dienes, regioselectivity, substituted indanes... 

Catalytic hydrothiolation and hydroselenation reactions are very useful for providing a wide variety of functionalized organosulfur and selenium compounds. For example, the palladium-catalyzed hydrothiolation of conjugated enynes affords a series of 2-(phenylsulfanyl)-1,3-dienes regioselectively in good yields (Scheme 29) [100]. 

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