Cyclic diorganozincs

Scheme 3 The stereoselective preparation of chiral cyclic diorganozincs...

Figure 3.3. Scope of Cu/1-catalyzed asymmetric 1,4-addition of diorganozinc reagents to cyclic enones.

Aldehydes constitute useful electrophilic partners in such nickel-catalyzed reactions because the condensation between alkynes, aldehydes and diorganozinc compounds can afford stereodefined cyclic or acyclic ally lie alcohols67-69, as illustrated by the stereoselective cyclization of 111 to the corresponding 3-hydroxypyrrolidine (equation 46). Allenes or 1,3-dienes instead of alkynes also lead to similar reactivity70. 

Also, bis-1,3-dienes incorporate carbon dioxide in the presence of Ni(acac) and a diorganozinc reagent to afford cyclic carboxylic acids °. Conjugated dienemagnesium reagents react with acetone at -78 °C, followed by carbon dioxide at 0°C to form the spiro-y-lactone 34 in 68 % yield. ... 

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