Alkynide units

The —CH2CH2OH unit can be appended to an alkynide anion by reaction with ethylene oxide. 

A more recent example of a functionalized alkyne addition can be seen in Crimmin s synthesis of tala-romycin A (equation 42). ° This particular alkynide is an equivalent of the formyl acetone dianion and its use has been generalized as an entry into the spiroketal portion of the milbemycins (Scheme 20). This approach differs from the Hanessian strategy in that formation of the C(17> (21) pyran ring is constructed last, through use of the alkynic unit. 

Treatment of the bis-alkynide Zr(CCPh)Cp 2 with Zr(r 4-C4Hg)Cp 2 gives a compound with a delocalised metallacyclic system with, to a first approximation, two a,ir-alkynyl units.42 The single electron reduction of Ti(CCPh)Cp2 is reversible and gives an anion which although stable at -30°C, loses Cp at 25°C.43... 

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