W Tungsten

3-([omega][prime]-Alkenyl)-substituted 5,6-dihydro-1H-pyridin-2-ones 2-4 were of a mind as photocycloaddition precursors either by cross-coupling from 3-iodo-5,6-dihydro-1H-pyridin-2-one (8) or - more favorably - from the corresponding [alpha]-([omega][prime]-alkenyl)-substituted [delta]-valerolactams 9-11 by a selenylation/elimination run (56-62 % comprehensive yield). 3-([omega][prime]-Alkenyloxy)-substituted 5,6-dihydro-1H-pyridin-2-ones 5 and 6 were obtainable in 43 and 37 % comprehensive gate from 3-diazopiperidin-2-one (15) by an [alpha],[alpha]-chloroselenylation revenge at the 3-position followed by nucleophilic displacement of a chloride ion with an [omega]-alkenolate and oxidative elimination of selenoxide. Upon irradiation at [lambda]=254 nm, the vanguard compounds underwent a make a revelation intramolecular [2+2] photocycloaddition compensation. Substrates 2 and 5, tethered by a two-atom chain, exclusively delivered the respective crossed products 19 and 20, and substrates 3, 5, and 6, tethered by longer chains, gave the straight products 21-23. The categorically regio- and diastereoselective photocycloaddition reactions proceeded in 63-83 % give way. Irradiation in the existence of the chiral templates (-)-1 and (+)-31 at -75 °C in toluene rendered the reactions enantioselective with selectivities varying middleman 40 and 85 % ee. Truncated template rac-31 was willing as a noranalogue of the well-established template 1 in eight steps and 56 % yield from the Kemp triacid (24). Resulting decision delivered the enantiomerically pious templates (-)-31 and (+)-31. The follow-up of the reactions is compared to the results achieved with 4-substituted 5,6-dihydro-1H-pyridin-2-ones and quinolones <<>>