As described by Schreiner in “Tetrahedrane -- dossier of an unknown”, the parent tetrahedrane C4H4 is a long sought yet still elusive molecule. This can be ascribed to its high strain energy, ca. 136 kcal/mol, which was first circumvented by Maier using bulky tert-butyl substituents that encapsulate the reactive core via a “corset effect”. Given that phosphorus accomodates small bond angles more readily than does carbon, as exemplified by the elemental P4 molecule, it was logical to approach tetrahedrane stabilization via phosphorus incorporation. Accordingly, the group of Wolf prepared P2(CtBu)2 by dimerization of Becker’s phosphaalkyne tBuCP, whilst we synthesized P(CtBu)3 by generation and closure of a proposed phosphinidenoid [XP(CtBu)3](-) intermediate. Reasoning that a mixed C/P tetrahedrane RCP3 would experience the least strain amongst the possible C/P tetrahedranes, we targeted the parent HCP3 molecule, the synthesis of which required us to develop a new radical approach to the knitting together of a tetrahedrane core.

Alleviating strain in organic molecules by incorporation of phosphorus

ACS Spring 2022

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