Efficient and Regioselective 9-Endo Cyclization of α-Carbamoyl Radicals

Abstract

With the promotion of Lewis acid BF(3)•OEt(2), various N-(hex-5-enyl)-2-iodoalkanamides underwent efficient and regioselective 9-endo iodine-atom-transfer radical cyclization reactions at room temperature. The cyclized products were readily converted to the corresponding azonan-2-ones by reduction with Bu(3)SnH or to hexahydroindolizin-3(5H)-ones by treatment with aqueous Na(2)CO(3) in a one-pot, two-stage manner.

Synthesis of Bridged Diketopiperazines by Using the Persistent Radical Effect and a Formal Synthesis of Bicyclomycin

“…[22] Notably,t he product did not contain the TEMPO fragment, which is unusual, since secondary alkoxyamines usually do not undergo homolysis at this temperature. Precursor 17,w hich bears ap renyloxy group,f urnished the oxadiazabicyclo[3.2.2]nonanedione 18 through an efficient and clean 7-exo-trig cyclization.S ubstrate 19,w hich bears ah omoallyloxy group,u nderwent a9 -endo cyclization at 150 8 8Ct og ive DKP 20,w hich has af ive-atom bridge,i n moderate yield.…”

“…Precursor 17,w hich bears ap renyloxy group,f urnished the oxadiazabicyclo[3.2.2]nonanedione 18 through an efficient and clean 7-exo-trig cyclization.S ubstrate 19,w hich bears ah omoallyloxy group,u nderwent a9 -endo cyclization at 150 8 8Ct og ive DKP 20,w hich has af ive-atom bridge,i n moderate yield. [22] Notably,t he product did not contain the TEMPO fragment, which is unusual, since secondary alkoxyamines usually do not undergo homolysis at this temperature. Strong transannular strain in the 9-membered bridged system might be the reason for the facile TEMPOH elimination in this case.Alkoxyamine 21,which bears both allyl and prenyl groups,was designed as aprobe molecule to study the direct competition between the 7-exo and 8-endo cyclization modes.…”

Synthesis of Condensed Tetrahydroisoquinoline Class of Alkaloids by Employing TfOH‐Mediated Imide Carbonyl Activation

“…1,2,5,6‐Tetrahydropyrrolo[2,1‐ a ]isoquinolin‐3(10b H )‐one (4i): By following the general procedure, imide 3i (101 mg, 0.5 mmol) furnished the cyclized product 4i (67 mg, 72 % yield) as a colorless semisolid 3k. IR (KBr): $\tilde {\nu}$ = 2978, 2921, 2851, 1687, 1421, 1360, 1307, 1266, 1168, 755 cm –1 .…”

Rhodium‐Catalyzed Domino Hydroformylation/Double‐Cyclization Reaction of Arylacetylenecarboxamides: Diastereoselectivity Studies and Application in the Synthesis of 1‐Azabicyclo[x.y.0]alkanes

“…[8] Therefore, the physiological activities of azabicyclic compounds have prompted many syntheticc hemistst od evelop various elegant approaches for their synthesis. [9] In ap reliminary communication, we demonstrated ad omino reaction strategy that employed allyl amides for the preparation of indolizidines. [4] Herein, we report af ull account of our findings, which includes an investigation of the reaction's scope and limitations, its application to the synthesis of natural alkaloids, and arationale for the differenceinr eactivities of isomeric homoallyl amide and3 -butenamide in this process.…”