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A new method for regioselective zincations of challenging N-heterocyclic substrates such as pyrimidines and pyridazine was reported using bimetallic bases TMPZnX•LiX (TMP = 2,2,6,6-tetramethylpiperidyl; X = Cl, Br). Reactions occurred under mild conditions (25-70 °C, using 1.75 equivalents of base without additives), furnishing 2-zincated pyrimidines and 3-zincated pyridazine, which were then trapped with a variety of electrophiles. Contrasting with other s-block metalating systems, which lack selectivity in their reactions even when operating at low temperatures, these mixed Li/Zn bases enabled unprecedented regioselectivities that cannot be replicated by either LiTMP nor Zn(TMP) 2 on their own. Spectroscopic and structural interrogations of organometallic intermediates involved in these reactions have shed light on the complex constitution of reaction mixtures and the origins of their special reactivities.

α-Bromolactones bearing a substituent in the β-position undergo a highly trans-diastereoselective arylation with arylzinc chlorides in the presence of 10–20% CoCl2 and 10–20% PPh3 in THF under mild conditions (25 °C, 16 h) leading to optically enriched α-arylated lactones and protected aldol products (99% ee) in 52–96% yield. The synthetic utility of this arylation was demonstrated by the stereoselective preparation of an artificial rotenoid MOM-protected munduserol derivative.

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