Ring opening reactions with nitrogen nucleophiles

Reaction with Nitrogen Nucleophiles. The acid-catalyzed reaction of primary, secondary, and tertiary amines with ethyleneimine yields asymmetrically substituted ethylenediamines (71). Steric effects dominate basicity in the relative reactivity of various amines in the ring-opening reaction with ethyleneimine (72). The use of carbon dioxide as catalyst in the aminoethylation of aliphatic amines, for which a patent application has been filed (73), has two advantages. First, the corrosive salts produced when mineral acids are used as catalysts (74,75) are no longer formed, and second, the reaction proceeds with good yields under atmospheric pressure. 

A ring opening reaction of (1-lactams promoted by methoxide generated nitrogen nucleophiles in situ that subsequently added to proximal allenes producing trisubstituted pyrroles <06CC2616>. In the event, treatment of (3-lactam 3 with MeONa led to pyrrole-2-acetic ester 4 after cleavage of the amide bond, 5-exo-dig cyclization, and loss of methanol. The sequence was notable as no metal catalyst was required. 

In general, the reaction of unsaturated 5(4//)-oxazolones 497 with nitrogen nucleophiles effects ring opening to give the corresponding unsaturated acylamino amides 498 (Scheme 7.158). Depending on the nucleophile, for example, amines, hydrazines, oximes, and so on, the products obtained can be cyclized and this process allows the synthesis of a wide variety of new heterocyclic compounds. 

Most of the ring-opening reactions of aziridines may be formulated -.as nucleophilic substitution reactions, in which one of the oarbon- nitrogen bonds is broken and a new bond with carbon is formed. In this section, ring-opening reactions are classified ou the basis of the element which is joined to the carbon atom in the newly formed bond of the reaction product. ... 

Another novel class of oxonium dications involves the superacid-promoted ring opening reactions of oxazolines and related conversions.61 Oxazolines are well known for their ability to react with strong nucleophiles (i.e. alcohols) when protonated at the ring nitrogen 62 It was shown that the dicationic species (161 or 162) are capable of reacting with weak nucleophiles such as benzene (eq 52). 

Nitrogen-based nucleophiles continue to remain popular in ring-opening reactions of aziridines. a-Substituted-a-methoxycarbonyl-V-nosylaziridines were opened with a variety of functionalized amines to provide access to enantiopure a,a -disubstituted (3-lactam scaffolds for ditopic peptidomimetics <07OL101>. A related intramolecular regioselective 3,Y-aziridine ring opening with an a-amino functionality was reported in the synthesis of... 

Nitriles can act as nitrogen nucleophiles in aziridine ring-opening reactions. Two examples are shown in Scheme 25 in which a formal [3-1-2] cycloadduct is the final product. Tosylaziridine 147 was reacted with benzoni-trile and BF3 OEt2 catalysis to produce the r-fused imidazoline 148 <2004TL1137>. The utility of the reaction is limited in the case of cyclic aziridines to benzofused aziridines and either aryl or benzyl nitriles. It was also found that the reaction required stoichiometric BF3. Lesser amounts of Lewis acid reduced the chemical yield drastically. 

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