Catalysis of the Cope and Claisen rearrangements

Chimmitecan, a Novel 9-Substituted Camptothecin, with Improved Anticancer Pharmacologic Profiles In vitro and In vivo

“…Chimmitecan was produced by etherization of 10-hydroxy-camptothecin with allyl bromide in the presence of a base (usually K 2 CO 3 ) followed by a Claisen rearrangement (12). The purity was 98.6% as determined by high-performance liquid chromatography.…”

Rearrangement Reactions for the Synthesis of Some Oxa- and Aza-tricyclic Rings Heterocyclic Compounds

“…A Claisen rearrangement of ether 9c yielded intermediate 10b which then underwent a homo [1,5] [14,15]. Several geranyl phenyl ethers were prepared and tested for inhibition of insect growth.…”

“…However, thermal rearrangement of this ether (3b) yielded an unexpected product (4b). The formation of this compound could be the following: the initial step a [3,3]-sigmatropic rearrangement of the ether (3b) afforded intermediate 4c which then underwent a homo [1,5]-H shift to yield compound 6 [Scheme 2]. A [1,5]-H shift on compound 6 led to the formation of compound 4b which by intermolecular cyclization furnished 5b in excellent yield.…”

Synthesis and biological evaluation of fused oxepinocoumarins as free radicals scavengers

“…The Claisen rearrangement of 8-allyloxycoumarin (16) 48 in refluxing ethyleneglycol resulted in 7-allyl-8 -hydroxycoumarin (17) (89%) 48 . The later allylated with allyl bromide and gave 7-allyl-8-(allyloxy)coumarin (18) (82%), which by RCM reaction with the catalyst 6 (6.9 mol%, added in three portions over 12 h) furnished the dihydrooxepin derivative 19 in 83% yield (Scheme 3).…”

“…In particular, coumarins fused with a ring containing an O-atom such as furocoumarins and pyranocoumarins are important as photochemotherapeutic [4][5][6][7][8][9][10] agents and exhibit antitumorial 11 , antifungal 12 , insecticidal 12 , anticancer 12 , anti-HIV 6,13 , anti-inflammatory 3,14 , and antioxidant 3,14 activities. The synthesis of those coumarins has been achieved mainly by formation of furan or pyran ring starting from hydroxycoumarins and using the tandem Claisen rearrangement-cyclization reaction 15,16 of the intermediate propargyloxy-or allyloxycoumarins [17][18][19][20][21] . The Ru-catalyzed ring-closing metathesis (RCM) [22][23][24][25][26] has been applied in the synthesis of furan and pyran ring during the last decade 25,[27][28][29][30] and especially in the synthesis of fused furo-or pyranocoumarins 25,27,29 .…”