The intramolecular amination of allenes

Abstract

Rhodium-bound nitrenoids are trapped by tethered allenes generating acyloxy-enamines, aminocyclopropanes, and methylene aziridines. The aminocyclopropanes undergo substitution of the acetoxy group by a variety of nucleophiles.

Oxidative Allene Amination for the Synthesis of Azetidin‐3‐ones

“…Placing ab ulky tert-butyl group at C1 of the homoallenic sulfamate 1 (Scheme 3) did not completely prevent aziridination yielding a2 :1 mixture of exo-and endocyclic bicyclic methyleneaziridines 2a and 2b. [11] Manipulation of electronic effects proved to be abetter strategy,as placement of a tert-butyldimethylsilyl (TBS) group at C1 of 3 resulted in exclusive aziridination of the distal double bond to 4 using av ariety of dinuclear Rh II catalysts.T he superior regioselectivity exhibited by silylated allene 3 was attributed to stabilizing electronic interactions between the CÀSi bond and the p-bonds of the allene (Scheme 3, bottom). As the aziridine begins to form anew C À Nbond at the distal double bond of the allene,the C À Si bond becomes co-planar with the p-orbitals,a llowing hyperconjugation to stabilize the developing positive charge at the b carbon.…”

Nitrene Chemistry in Organic Synthesis: Still in Its Infancy?

“…Based on the aforementioned hypotheses, the Blakey group has further envisaged the application of rhodiumnitrene chemistry to allenes in order to produce 2-amidoallyl cations; [54] an analogous study was also carried out in parallel by Robertson et al [55] Because of the absence of general methods for their preparation, these synthons have received little attention so far, in contrast to their carba and oxa analogues, namely trimethylenemethane and 2-oxyallyl cations. This gap, however, was filled by the use of nitrenes generated from sulfamates.…”

“…Robertson et al have demonstrated that the strained N,O-acetals can react further with various nucleophile such as hydrides and malonate anions. [55] Both research groups have reported that the overall transformation is sensitive to steric effects. The introduction of bulkier iPr or Ph substituents on the allene favors the formation of products such as 66, resulting from a formal oxyamidation process (Scheme 16).…”

“…The introduction of bulkier iPr or Ph substituents on the allene favors the formation of products such as 66, resulting from a formal oxyamidation process (Scheme 16). [55] Even more unexpectedly, the presence of a tert-butyl group leads to the sole formation of regioisomeric methylene aziridines 68 and 69. This type of influence of the substitution has also been pointed out by Schomaker et al in their work related to allene functionalization.…”

Novel Cyclization Reactions of Aminoallenes

“…Independently, Robertson’s group has studied analogous reactions on allenyl sulfamates, being rhodium‐bound nitrenoids trapped by the allene moiety to generate acyloxy‐enamines, aminocyclopropanes, and methyleneaziridines 69. This group also developed the the Rh(II)‐catalyzed intramolecular aziridination of allenyl‐substituted N ‐tosyloxycarbamates leading to bicyclic methylene aziridines, which undergoes interesting chemistry including formal S N V ring‐opening and acid‐mediated [4+3] cycloaddition 70…”