An efficient method for the diastereo- and enantioselective construction of vicinal all-carbon quaternary stereocenters through palladium-catalyzed decarboxylative cycloaddition of vinylethylene carbonates with activated Michael acceptors was developed. By using a palladium complex generated in situ from [Pd2(dab)3]⋅CHCl3 and a phosphoramidite ligand as a catalyst under mild reaction conditions, the process provides multifunctionalized tetrahydrofurans bearing vicinal all-carbon quaternary stereocenters in high yields with a high level of absolute and relative stereocontrol.

Exposure of aromatic carboxamides 1e-1m, heteroaromatic carboxamides 1n-1p, and r,β-unsaturated carboxamides 1q-1s to 1,1dimethylallene in the presence of the a cationic iridium complex derived from [Ir(cod) 2 ]BAr F 4 and rac-BINAP results in direct C-H prenylation to furnish adducts 2e-2m, 2n-2p, and 2q-2s, respectively, in good isolated yields as single isomers.Enzymatic prenyl transfers are heavily trafficked biosynthetic pathways, 1 yet synthetic catalysts for C-H prenylation are unknown. [2][3][4] Having recently developed protocols for catalytic carbonyl prenylation employing 1,1-dimethylallene as the prenyl donor, 5 catalytic ortho-C-H insertion of 1,1dimethylallene was viewed as a potential strategy for the direct prenylation of aryl C-H bonds. Due largely to the pioneering efforts of Murai, 6 Lewis base-directed catalytic C-H activation initiated olefin insertions, and alkyne inser-

An efficient method for the enantioselective construction of tertiary C-O bond via asymmetric allylic substitution of racemic vinylethylene carbonates with water and alcohols has been developed. Under the cooperative catalysis system of an in situ generated chiral palladium complex and boron reagent in mild conditions, the process allowed rapid access to valuable tertiary alcohols and ethers in high yields with complete regioselectivities and high enantioselectivities. This protocol represented the first example of direct enantioselective formation of a tertiary C-O bond with water as an oxygen donor. The synthetic utilities of the process have been demonstrated by the elaboration of the products into key intermediates of biologically relevant agents, and chiral tertiary cyclic ethers could also be provided through the sequential reactions of the allylic etherification and ring-closing metathesis.

An efficient method for the enantioselective construction of tertiary vinylglycols through a palladium-catalyzed asymmetric decarboxylative cycloaddition of vinylethylene carbonates with formaldehyde was developed. By using a palladium complex generated in situ from [Pd2(dba)3]⋅CHCl3 and a phosphoramidite ligand as a catalyst under mild reaction conditions, the process allows conversion of racemic 4-substituted 4-vinyl-1,3-dioxolan-2-ones into the corresponding 1,3-dioxolanes, as methylene acetal protected tertiary vinylglycols, in high yields with good to excellent enantioselectivities.

Enantioselective transfer hydrogenation of carbonate 1a in the presence of aromatic, allylic or aliphatic alcohols 2a-2i employing a cyclometallated iridium C,O-benzoate derived from allyl acetate, 4-cyano-3-nitrobenzoic acid and (S)-SEGPHOS delivers products of (hydroxymethyl) allylation 4a-4i in good isolated yields (60-74%), good anti-diastereoselectivities (5:1-10:1 dr) and exceptional levels of enantiocontrol (93-99% ee). Under identical reaction conditions, but in the presence of isopropanol, aldehydes 3a-3i are converted to an equivalent set of adducts 4a-4i in good isolated yields (58-74%), good anti-diastereoselectivities (4:1-14:1 dr) and exceptional levels of enantiocontrol (95-99% ee). Thus, identical sets of adducts 4a-4i are produced with equal facility from the alcohol or aldehyde oxidation level. These studies represent the first general method for enantioselective carbonyl (hydroxymethyl)allylation, a process that has no highly stereoselective counterpart in conventional allylmetal chemistry.The hydroxymethyl 1,3-diol motif appears in numerous natural products,1 -4 yet asymmetric methods for carbonyl (hydroxymethyl)allylation are largely unexplored. 5-7 In most cases, catalytic carbonyl hydroxymethylation has been accomplished through umpolung of palladium π-allyl complexes derived from 2-butene-1,4-diol carboxylates5 or vinyl epoxides6 in combination with metallic reductants, such as SnCl 2 or InI. However, control of regio-and diastereoselectivity has proven challenging. Nakajima, as well as Cozzi and Umani-Ronchi, each report a single example of catalytic syn-(hydroxymethyl)allylation but only moderate mkrische@mail.utexas.edu. Supporting information available: Experimental procedures, spectral data for new compounds, including scanned images of HPLC traces, as well as 1H and 13C NMR spectra. This material is available free of charge via the internet at http://pubs.acs.org. We have found that chiral ortho-cyclometallated iridium C,O-benzoates catalyze carbonyl allylation,9a,b,e-h crotylation9c,f and tert-prenylation9d,f employing allyl acetate, α-methyl allyl acetate and 1,1-dimethylallene as allyl donors, respectively. For such C-C bond forming transfer hydrogenations, 10 alcohols function both as hydrogen donors and carbonyl precursors, enabling identical sets of carbonyl addition products to be generated from either the alcohol or aldehyde oxidation level. 1,2 In more recent work, it was found that use of the isolated iridium C,O-benzoate complex was essential for efficient reductive couplings of allylic gemdibenzoates. 9i This outcome prompted us to reexamine processes that failed using in situ generated catalysts, including reactions of allylic carbonates. NIH Public AccessHere, we report that complex (S)-I, which is modified by the chiral phosphine ligand (S)-SEGPHOS, 11 serves as a single-component catalyst for the coupling of cyclic carbonate 1a to alcohols 2a-2i to furnish (hydroxymethyl)allylation products 4a-4i in highly enantiomerically enriched form. Under similar conditi...