Functionalization of Styrenes by Copper‐Catalyzed Borylation/ ortho‐Cyanation and Silver‐Catalyzed Annulation Processes

Abstract

An efficient two-step method for the assembly of indanone derivatives starting from as imple vinyl arene has been developed. The sequence first involves addition of bis(pinacolato)diboron (B 2 pin 2 )a nd N-cyano-N-phenyl-pmethylbenzenesulfonamide (NCTS) to ab road range of styrenes by utilizing IMesCuCl as catalyst. This step simultaneously accomplishes hydroboration of the alkene and ortho cyanation of the benzeneunit. The products thus obtained are further functionalized by aA gNO 3 /Selectfluor-mediated coupling of the BPin and cyano functionalities to annulate anew five-membered ring. This combined two-step sequence provides av ersatile method for the site-selective derivatization of abroad range of vinyl arene substrates.

Copper‐Catalyzed Simultaneous Installation of Boryl and Carbonyl Functionalities to Unsaturated Hydrocarbons

“…Montgomery also reported a regioselective ortho ‐cyanation of styrene derivatives (Scheme 17). [24] The reaction of alkenes, B 2 pin 2 , and NCTS proceeded using IMesCuCl (IMes=1,3‐bis‐(2,4,6‐trimethylphenyl)‐imidazol‐2‐ylidene) as a catalyst in the presence of t BuOLi as a base in THF. The addition of 4 Å molecular sieves efficiently reduced a formal hydroborated byproduct.…”

Heterocyclization and Spirocyclization Processes Based on Domino Reactions of N‐Tosylhydrazones and Boronic Acids Involving Intramolecular Allylborylations of Nitriles

“…Pathwaya involves i) chair/twist-boat isomerization (G to G'), and ii)the a-attacko ft he alkenylboronic acid to the nitrile carbon atom through the transition state TS(G'-H).T his step featured av ery high energy barriero f6 2.2 kcal mol À1 that could not be reached, and therefore it was discarded. [17] Pathway bc onsists of i) 1,3-borotropic rearrangementt o give allylboronic acid J,i i) chair/twist-boat isomerization to J' and iii)intramolecular allylborylation of the cyano group throught he six-centered cyclic transition state TS(J'-H).T he transition state for the 1,3-borotropic rearrangement TS(G-J) featured the highest energy of this reactionp rofile, and therefore it could be considered the rate-determining step for the cyclization reaction. The activation barrierf or this step (DG act = 37.3 kcal mol À1 )i sv ery high, andt his might explain why these reactions proceed only at 120 8Ca nd under microwave irradiation.…”

Copper‐Mediated Oxidative Radical Addition/Cyclization Cascade: Synthesis of Trifluoromethylated and Sulfonated Quinoline‐2,4(1H,3H)‐diones

“…Nevertheless, the reaction might be successful if the unstable iminyl radical can be effectively trapped . Many transition metal complexes such as those of titanium, samarium, manganese, and silver were successfully employed for the radical addition onto nitriles. As part of our ongoing interest in radical cascade cyclizations, we report herein a Cu‐mediated oxidative radical addition/cyclization of o ‐cyanoarylacrylamides with sodium trifluoromethanesulfonate for the synthesis of trifluoromethylated quinoline‐2,4(1 H ,3 H )‐diones, where the cyclization was accomplished by an intramolecular addition of the carbon radical to the nitrile.…”