Riu MLY, Eckhardt AK, Cummins CC. Dimerization and Cycloaddition Reactions of Transient Tri-
tert-butylphosphacyclobutadiene Generated by Lewis Acid Induced Isomerization of Tri-
tert-butylphosphatetrahedrane.
J Am Chem Soc 2021;
143:13005-13009. [PMID:
34380311 DOI:
10.1021/jacs.1c06840]
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Abstract
Tri-tert-butylphosphatetrahedrane (1) is shown here to act as a synthon of isomeric tri-tert-butylphosphacyclobutadiene in the presence of a Lewis acid or transition-metal complex. When it is combined with a substoichiometric amount of triphenylborane, compound 1 forms a ladderane-type dimer of tri-tert-butylphosphacyclobutadiene in 72% isolated yield. Trapping of a generated intermediate was achieved by repeating the experiment in the presence of excess styrene (20 equiv) or ethylene (1 atm), and the corresponding [4 + 2] cycloadducts of tri-tert-butylphosphacyclobutadiene were isolated in 88% and 74% yields, respectively. The platinum complex (Ph3P)2Pt(C2H4) also reacts with 1 to form an orange η2 complex of tri-tert-butylphosphacyclobutadiene in 80% isolated yield. Additionally, we report a novel method for generating a phosphinidenoid species via fluoride-induced trimethylsilyl fluoride elimination, leading to an improved preparative procedure for 1 (182 mg, 33% isolated yield).
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