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Amination of [ClP(μ‐NtBu)]2 (1) using NH3 in THF gives the cyclophospha(III)zane dimer [H2NP(μ‐NtBu)]2 (2), in good yield. 31P NMR spectroscopic studies of the reaction of 1 with 2 in THF/Et3N show that almost quantitative formation of the cyclic tetramer [{P(μ‐NtBu)}2(μ‐NH)]4 (3) occurs. The remarkable selectivity of this reaction can (in part) be attributed to pre‐organisation of 1 and 2, which prefer cis arrangements in the solid state and solution. The macrocycle 3 can be isolated in yields of 58–67 % using various reaction scales. The isolation of the major by‐product of the reaction (ca. 0.5–1 % of samples of 3), the pentameric, host–guest complex [{P(μ‐NtBu)2}2(μ‐NH)]5(HCl)⋅2 THF] (4⋅2 THF), gives a strong indication of the mechanism involved. In situ 31P NMR spectroscopic studies support a stepwise condensation mechanism in which Cl− ions play an important role in templating and selection of 3 and 4. Amplification of the pentameric arrangement occurs in the presence of excess LiX (X=Cl, Br, I). In addition, the cyclisation reaction is solvent‐ and anion‐dependent. The X‐ray structures of 2 and 4⋅2 THF are reported.

In the synthesis of barium 3,5-dimethylpyrazolate, silicone joint grease and cyclo-(Me 2 SiO) 4 are cleaved and two O(SiMe 2 O) 2 2Ϫ bidentate chelating siloxane anions are coordinated above and below an unprecedented Ba 6 12Ϫ

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Snipping tool: Zn(OTf)2 is an efficient catalyst for selective cleavage of amides bearing a β‐hydroxyethyl group on the nitrogen atom. The mechanism involves an N,O‐acyl rearrangement and transesterification. This new catalytic system can be applied to sequence‐specific peptide bond scission at the amine side of a serine residue. Tf=trifluoromethanesulfonyl.