3- Methyl-2-pentene, photochemical reaction

The scope of this approach was widened by the observation of excellent enantioselectivities in intermolecular [2+ 2]-photocycloaddition reactions with various alkenes [62,71]. In the presence of an excess amount of alkene, 4-me thoxy-2-quinolone (57) was converted with high chemo- and regioselectivity to the exo and endo cyclobutanes 59 and 60. With 4-penten-1-ol (58a), allyl acetate (58b), methyl acrylate (58c), and vinyl acetate (58d), the exo diastereomers 59a-d were formed with high simple diastereoselectivity and in high yields (80-89%), Under optimized irradiation conditions (2.4 eq. of host 44 or ent-44, — 60°C), high enantiomeric excesses were achieved in all instances, as depicted in Scheme 22. These enantiomeric excesses are unprecedented for an intermolecular photochemical reaction. 

Solvent effects in the photochemical reaction of A -(2-phenyl-4-penten-l-oxy)-pyridine-2(l//)-thione and Bu3SnH have been studied [36]. Neither the use of tert-butyl benzene, chlorobenzene, bromobenzene, anisole, cyclohexane, tetrahydrofuran, nor ethanol leads to a significant change in yields and selectivities for the formation of 2-methyl-4-phenyl tetrahydrofuran (16) (50-70%, cis/trans 88 12),... 

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