Highly stereocontrolled synthesis of trans-enediynes via carbocupration of fluoroalkylated diynes

Abstract

SummaryTreatment of readily prepared (Z)-6-benzyloxy-1,1,1,2-tetrafluoro-6-methyl-2-hepten-4-yne with 1.5 equiv of LHMDS in −78 °C for 1 h gave the corresponding trifluoromethylated diyne in an excellent yield. This diyne was found to be a good substrate for the carbocupration with various higher-ordered cyanocuprates to give the corresponding vinylcuprates in a highly regio- and stereoselective manner. The in situ generated vinylcuprates could react very smoothly with an excess amount of iodine, the vinyl iodides being obtained in high yields. Thus-obtained iodides underwent a very smooth Sonogashira cross-coupling reaction to afford various trans-enediynes in high yields.

Trifluoromethylated Internal Alkynes: Versatile Building Blocks for the ­Preparation of Various Fluorine-Containing Molecules

“…After several trials, we found that the dehydrofluorination of tetrafluorinated enynes 13 proceeded efficiently (Scheme 7). 18 Thus, treatment of 2,3,3,3-tetrafluoro-1-iodo-1-propene (5) with a terminal alkyne (1.2 equiv) and triethylamine (Et 3 N) (1.5 equiv) in the presence of 5 mol% of palladium(II) acetate [Pd(OAc) 2 ] and 10 mol% each of triphenylphosphine…”

“…These intermediates reacted smoothly with water, leading to the trisubstituted alkenes 31a in high to excellent yields, whereas they reacted only with limited carbon electrophiles, such as allyl, crotyl, methallyl, and propargyl bromides, but not benzyl bromide, due to the low re- The carbocupration of CF 3 alkynes is also a powerful tool in the stereoselective synthesis of CF 3 -substituted transenediynes, as shown in Scheme 17. 18 Thus, CF 3 -containing diynes 12 reacted smoothly with various higher-ordered cyanocuprates to give the corresponding vinyl copper intermediates. In all cases, the re-actions proceeded in a highly selective cis-addition manner.…”