Nitrene Chemistry in Organic Synthesis: Still in Its Infancy?

Abstract

The element nitrogen is essential to life. Considerable attention is thus paid to the development of synthetic methods for its introduction into molecules. Nitrenes, long regarded as highly reactive but poorly selective species, have recently emerged as useful tools for the formation of C-N bonds. Practical metal-catalyzed protocols are now available for the preparation of amines through either the aziridination of alkenes or the C-H amination of alkanes. Recent results highlighted in this Minireview suggest that synthetic nitrene chemistry is maturing with a wider scope not limited to these two reactions.

Highly sialylated recombinant human erythropoietin production in large‐scale perfusion bioreactor utilizing CHO‐gmt4 (JW152) with restored GnT I function

“…Transition metal‐catalyzed/mediated nitrene/imide transfer or insertion reactions is an appealing strategy for the construction of CN bonds,1 and the common sources of nitrogen atom/group in these reactions include: 1) iminoiodinanes (such as PhINTs),1b,c,e,f,h–k,m,n or in situ formed iminoiodinanes via oxidation of amides such as sulfonamides,1b,e,f,h,i,k sulfamates,1a,b,e,f,h,i,k–n and carbamates1a,b,e,f,h,k,l,m with hypervalent iodine reagents such as PhI(OR) 2 , 2) oxidizing amide salts such as bromamine‐T1c,h,i and chloramine‐T,1c 3) hydroxylamine derivatives such as N ‐sulfonyloxycarbamate,1a,b,k and 4) organic azides with examples of sulfonyl azides,1c,d,g,h,i,k,n phosphorazidates,1c,d,g,h,i,k and aryl azides1c,d,g–k,m,n (Figure 1). Primary amines without bearing strong electron‐withdrawing group(s) (such as amides) could also be used as nitrogen source for oxidative CN bond forming reactions.…”

Bis(2,2-dimethylpropanoato - κ-O)phenyl-iodine

“…Recent results, however, tend to prove that this chemistry should be more versatile. 44 Whereas unprecedented cascade reactions have been described from alkynyl sulfamates with PhI(OAc) 2 to give complex polycyclic sulfamates, 45 PhI(OCO t Bu) 2 has proved to be optimal for performing a similar sequence from allenyl sulfamates. This affords aminocyclopropane derivatives in good to very good yields (eq 26).…”

Synthesis of azasilacyclopentenes and silanols via Huisgen cycloaddition-initiated C–H bond insertion cascades

“…11 Pioneering work from Blakey showed nitrene/alkyne cascades proceeded through an endo-cyclization with the alkyne to the postulated vinyl cation/metalloenamine 10a , which potentially could rearrange to the α-iminometallocarbene 10b or react directly (Scheme 2). 12 Importantly, metallocarbene 12 could not be accessed via that approach, and α-diazoimines are difficult to synthesize.…”