Bromoallenes as Synthetic Equivalents of Allyl Dications: Synthesis of Medium‐Sized Nitrogen Heterocycles through the Cyclization of Bromoallenes in the Presence of a Palladium(0) Catalyst and an Alcohol

Abstract

Eine hoch regio‐ und stereoselektive Cyclisierung zum Aufbau mittelgroßer Stickstoffheterocyclen wurde entwickelt (siehe Schema), die darauf beruht, dass Bromallene in Gegenwart eines Palladium(0)‐Katalysators und eines Alkohols als Äquivalent für ein Allyldikation eingesetzt werden können. Der intramolekulare nucleophile Angriff erfolgt ausschließlich am mittleren Kohlenstoffatom der Allen‐Einheit.

Bromoallenes as Allyl Dication Equivalents in the Presence or Absence of Palladium(0): Direct Construction of Bicyclic Sulfamides Containing Five‐ to Eight‐membered Rings by Tandem Cyclization of Bromoallenes

“…These results demonstrate that bromoallene 9 a can act as allyl dication equivalent even in the absence of palladium (0). However, it should be clearly noted that, in the medium-ring formation, [14] the palladium catalyst is essential for successful conversion. For example, treatment of bromoallene 13 with in situ-generated NaOMe in the presence of [PdA C H T U N G T R E N N U N G (PPh 3 ) 4 ] gave the seven-membered ring 14 [14c] in 76 % yield, as a result of the first intramolecular nucleophilic attack on the central carbon atom of the allene moiety followed by the second nucleophilic reaction by methoxide.…”

“…[10,11] Currently, reactions of bromoallenes are attracting much interest due to their interesting chemical properties associated with the cumulated double bonds and bromine substituent. [12] However, except for our recent study on ring-forming reactions, [13,14] all the reactions of bromoallenes reported to date are intermolecular reactions. [15,16,17,18] In our previous work, [14] we found that bromoallenes A can act as allyl dication equivalents B in the presence of palladium(0) and alcohol, which are extremely useful for the synthesis of mediumAbstract: A highly regioselective synthesis of bicyclic sulfamides is described.…”

“…[12] However, except for our recent study on ring-forming reactions, [13,14] all the reactions of bromoallenes reported to date are intermolecular reactions. [15,16,17,18] In our previous work, [14] we found that bromoallenes A can act as allyl dication equivalents B in the presence of palladium(0) and alcohol, which are extremely useful for the synthesis of mediumAbstract: A highly regioselective synthesis of bicyclic sulfamides is described. Based on our recent discovery that bromoallenes can act as allyl dication equivalents in the presence of a palladium catalyst and alcohol, we investigated tandem cyclization of bromoallenes bearing a sulfamide group.…”

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

“…These results are in good agreement with the computational investigation by Prof. Ando. 130) [152][153][154] Medium-sized heterocycles are an extremely important class of compounds, the structural units of which are commonly found within the framework of a variety of natural products. 155) In particular, seven-and eightmembered heterocycles are constituents of a number of compounds with interesting pharmacological properties.…”

Difluoroallenyl Bromide as a Wide‐Ranging Difluoromethylene Cation Equivalent: SN2 Substitution of Difluoropropargyl Bromide through Sequential SE2′ and SN2′ Reactions

“…[19] We had reported earlier that the preformed indium propargyl complex 4 [20] yielded fluoroallenyl alcohol 5 when treated with a reactive electrophile, such as aqueous formaldehyde (Scheme 3). [21] Less reactive electrophiles, such as benzaldehyde or imines, produced homopropargyl alcohol or amines.…”