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A precatalyst of FeCl2 and iminopyridine was activated in situ by a combination of diethylzinc and magnesium bromide etherate; it catalyzed the reductive cyclization of 1,6-enynes to give pyrrolidine and tetrahydrofuran derivatives from N- and O-tethered 1,6-enynes. The scope of the transformation was explored.

A titanium-mediated, hydroxy-directed reductive coupling reaction of propargylic alcohols and aldehydes/ketones is described. Excellent diastereoselectivity and synthetically useful yields have been obtained for a range of substrates. This transformation has enabled a highly convergent three-component approach to syn-1,3-diols using (trimethylsilyl)acetylene as a C1 linchpin.

An efficient synthesis of the C1-C12 fragment of iriomoteolide 1a has been accomplished via sequential application of two catalytic, asymmetric, vinylogous aldol reactions: a catalytic vinylogous aldol reaction was used to enantioselectively introduce the C5-C8 segment, and a second catalytic vinylogous aldol reaction was used to install the remaining two stereocenters and a stereodefined alkene in the form of an alpha,beta-unsaturated delta-lactone in one step.

[reaction: see text] Deprotonation of 2-hydroxycyclooctanone followed by exposure to an allylic or benzylic halide proceeds very selectively to give the product of C-alkylation. The effect of Delta(5,6)-unsaturation is to promote instead the formation of the O-alkylated derivative. This crossover in kinetic preference is attributed to an inability of the olefinic system to attain a conformation conducive to proton abstraction at C-2.