Single crystal structure analysis of the two ENHIs 1l and 2a (Figure ) revealed the expected T-shape structure of the hypervalent iodine center (N-I-O angles of 165.78° for 1l and 164.77° for 2a) and an expected longer N-I distance in the pseudocyclic salt (2.517 Å) compared to the cyclic iodane (2.431 Å). While the alkyne group of the pseudocyclic salt 1l is nearly in plane with the aromatic system, 2a is significantly twisted with a C1-I1-N1-C10 dihedral angle of 17.26°. This twist was previously observed for other bis-N-heterocyclic substituted-λ 3iodanes. Additionally, in 2a 1/6 equiv. of NaOTf is included in the crystal structure (see ESI). After the successful synthesis of a range of new (pseudo)cyclic ENHIs, their potential in electrophilic alkynyl transfer reactions was investigated. First, a relative performance test of all ENHIs was accomplished on the alkynylation of β-ketoester 4a via the in situ formed free alkynyl-NHI (Table ). This reaction has been previously investigated by Waser and coworkers using TIPS-EBX and TIPS-EBZ reagents. Starting with the triazole 1a, quantitative formation of the desired product 5a could be observed after 1 h (entry 1). The cyclic derivative 2a gave 5a in 79% yield, which could be significantly increased to 94% after a prolonged reaction time of 18 h (entries 2-3). The non-methylated triazole salt 1b gave an