Diastereo- and Enantioselective Intramolecular [2+2] Photocycloaddition Reactions of 3-(ω′-Alkenyl)- and 3-(ω′-Alkenyloxy)-Substituted 5,6-Dihydro-1<i>H</i>-pyridin-2-ones
作者:Dominik Albrecht、Florian Vogt、Thorsten Bach
DOI:10.1002/chem.200902616
日期:2010.4.12
37 % overall yield from 3‐diazopiperidin‐2‐one (15) by an α,α‐chloroselenylation reaction at the 3‐position followed by nucleophilic displacement of a chloride ion with an ω‐alkenolate and oxidative elimination of selenoxide. Upon irradiation at λ=254 nm, the precursor compounds underwent a clean intramolecular [2+2] photocycloaddition reaction. Substrates 2 and 5, tethered by a two‐atom chain, exclusively
3-(ω' -烯基) -取代的5,6-二氢- 1 H ^ -吡啶-2-酮2 - 4制备为前体光环通过从3-碘-5,6-二氢-1-交叉耦合ħ -吡啶-2-酮(8)或-更优选-从相应的α-(ω' -烯基) -取代的δ-戊内酰胺9 - 11由硒化/消除序列(56-62%总产率)。3-(ω'-链烯氧基)-取代的5,6-二氢-1 H-吡啶2-2-酮5和6可从3-重氮哌啶-2-酮的总产率中获得43%和37%(15)通过在3位的α,α-氯硒基化反应,然后用ω-链烯酸酯进行氯离子的亲核置换并氧化消除亚硒酸盐。在λ= 254nm处照射时,前体化合物进行了干净的分子内[2 + 2]光环加成反应。基板2和5,由两个原子的链拴,排他地输送的相应交叉产品19和20,和基片3,5,和6,通过拴系更长的链,得到直制品21 - 23。完全的区域和非对映选择性光环加成反应的产率为63-83%。在手性模板(−)- 1和(+)‐