First Palladium-Catalyzed Aziridination Reaction of Amino Allenes

Thermal Intramolecular [2+2] Cycloaddition of Allenenes and Allenynes: Diastereoselective Access to Bicyclic Nitrogen Heterocycles

“…[2] Only limited examples of the intramolecular [2+2] reaction of the distal allenic double bond to give 3 have been reported to date, which used a special class of allenes such as allene carboxylates, [8] allenyl sulfones, [9] difluoroallenes, [10] b-lactam-tethered allenes, [11] or diyne-diallenes. [12] In the course of our efforts toward the development of a new methodology for the synthesis of heterocyclic compounds by the transition-metal-catalyzed cyclization of allenes, [4,13] we found that the thermal cycloaddition of simple allenes with an additional multiple bond proceeds by simply heating the allenenes or allenynes in the absence of any catalyst. Herein, we present an intramolecular [2+2] cycloaddition of unactivated allenes to form distal adducts of type 3, which constitute an important class of compounds in synthetic [14] and natural product chemistry.…”

Vinylaziridines in Organic Synthesis

“…We also reported a highly stereodivergent synthesis of sterically congested cisand trans-alkenylaziridines 61 and 65 (Scheme 2.19) [33]. Whereas treatment of the methyl carbonates 59 with catalytic amounts of Pd(PPh 3 ) 4 in THF or 1,4-dioxane predominantly affords the corresponding thermodynamically more stable 2,3-cis-2-alkenylaziridines 61 (up to 99:1), treatment of the allylic mesylates 62 with sodium hydride in DMF exclusively yields the thermodynamically less stable trans-2-alkenylaziridines 65 (>99:1).…”

“…In particular, cyclization of amino allenes has become quite a useful methodology for the synthesis of five-or six-membered azacycles [35]. In contrast, ring-closure of amino allenes to yield aziridines was unknown until 1999, when Ohno, Ibuka, and coworkers found that the palladium-catalyzed reaction between the a-amino allene 66 and iodobenzene in the presence of K 2 CO 3 at reflux in 1,4-dioxane exclusively yielded the corresponding 2,3-cis-and trans-2-alkenylaziridines 68 and 69, respectively, each bearing a phenyl group on the double bond (Scheme 2.20) [36]. Interestingly, the reaction in DMF at around 70°C afforded the corresponding 3-pyrroline derivative 70 as the sole isolable product.…”

Development of Useful Reactions Involving Tandem Cyclizations Based on the Novel Reactivities of Allenic Compounds

“…b) Isolated yields. formation of small rings, including cyclopropanes, 58,59) by intramolecular nucleophilic attack onto the allenic moiety is well documented, [32][33][34][55][56][57] direct synthesis of bicyclic cyclopropanes by the reaction of allenes with an additional multiple bond is unprecedented. Similarly, the reaction of allenenes 108 and 109 under the identical reaction conditions gave 111b and 112 in 57-59% yields.…”