COUPLING OF ALKYNYL(2,4,6-TRI-TERT-BUTYLPHENYL)PHOSPHANES WITH CUPROUS CHLORIDE

Coupling of alkynyl(2,4,6-tri-tert-butylphenyl)phosphanes 2 with n-but yllithium and cuprous chloride gives 3,4-diphospha-1,5-hexadiynes 3 or cuprous chloride complexes 8 of 3,4-bis(phosphinidene)cyclobutenes 5, depending on the bulkiness of the substituent at the triple bond. The exclusive formation of racemic 3,4-diphospha-1,5-hexadiynes 3, which was proven by P-31- and C-13-NMR spectroscopy, explains the stereosele ctive rearrangement to only symmetrical cyclobutenes 5.