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In order to evaluate the dependence of the steric effects of alkyl groups on the crowding of the double bond, bromination rate constants of adamantylidenealkanes 1, Ad=CRR' with R = H or Me and R'= H, Me, i-Pr, t-Bu, or neo-Pe, and similarly substituted isopropylidenealkanes 2, Me2C=CRR', are compared.Since the bromination rate of 1a (R = R'= H) is that expected by considering only the polar effect of two gem-isopropyls, the adamantyl group in 1, like the gem-methyls in 2, clearly does not exhibit anyl intrinsic steric effect.However, branched substituents R'slow thereaction of 1 twice as much as that of 2.This difference between the effects on 1 and 2 does not arise from differences in the stereoarrangement of R and R'since, according to MM2 calculations, they adopt exactyl the same conformation in both alkene series.Comparision of the bromination rates of 1 in methanol with those measured in acetic acid reveals that the solvent effect (kMeOH/kAcOH about 4) is markedly smaller than that (kMeOH/kAcOH = 25) on linear alkenes, which suggests that greater steric retardation in adamantylidenealkanes can be attributed to mechanistic changes: inhibition of nucleophilic solvent assistance in the ionization step and/or return resulting from a slow product-forming step.

Molybdenum and tungsten oxo 2-adamantylidene (Adene) complexes that contain two nonafluoro-tert-butoxide (ORF9) ligands have been prepared through addition of 2-methylene-or 2-ethylideneadamantane to neophylidene or neopentylidene complexes. The isolated oxo complexes include W(O)(Adene)(ORF9)2(PPh2Me) (1W), W(O)(Adene)(ORF9)2 (2W), W(O)(Adene)(2,5-dimethylpyrrolide)2 (3W), W(O)(Adene)(2,5-dimethylpyrrolide)(2,6-dimesitylphenoxide) (4W), Mo(O)(Adene)(ORF9)2(PPhMe2) (1Mo), and Mo(O)(Adene)(ORF9)2 (2Mo). Compound 2W is a dimer that contains unsymmetrically bridging oxo ligands; it dissociates readily and reversibly into monomers, especially in the presence of a donor such as THF. In contrast, 2Mo is a monomer. Both 2W and 2Mo are remarkably stable thermally. The pale-blue complexes Mo(Adene)(ORF9)2Cl2 (5Mo) and W(Adene)(ORF9)2Cl2 (5W) are formed upon addition of PCl5 to 2Mo and 2W, respectively. The oxo complexes are reactive olefin metathesis initiators, while 5Mo and 5W are relatively poor initiators. We ascribe the thermal stability of 2Mo and 2W to resistance of the 2-adamantylidene ligands to couple bimolecularly, to the absence of an α-hydrogen in the alkylidene, or both.

An efficient synthetic protocol involving iron-catalyzed cross-coupling reactions between organolithium compounds and alkenyl iodides as key coupling partners was achieved. More than 30 examples were obtained with moderate to good yields and high stereospecificity. Gram-scale and synthetic applications of this procedure are recorded herein to demonstrate its feasibility and potential utilization.

We report that a regioselective reductive transposition of primary allylic bromides is catalyzed by a biphilic organophosphorus (phosphetane) catalyst. Spectroscopic evidence supports the formation of a pentacoordinate (σ5-P) hydridophosphorane as a key reactive intermediate. Kinetics experiments and computational modeling are consistent with a unimolecular decomposition of the σ5-P hydridophosphorane via a concerted cyclic transition structure that delivers the observed allylic transposition and completes a novel PIII/PV redox catalytic cycle. These results broaden the growing repertoire of reactions catalyzed within the PIII/PV redox couple and suggest additional opportunities for organophosphorus catalysis in a biphilic mode.

The widely available carbonyl compounds react with Grignard reagents in the presence of diethyl phosphite to give the corresponding olefins in good to excellent yields: A range of conjugated dienes, terminal olefins, multisubstituted-alkenes and conjugated enynes could be readily obtained by the method in mild conditions.

There is provided a method for obtaining an alkyladamantyl ester efficiently by distilling and purifying a crude alkyladamantyl ester containing impurities which decompose the alkyladamantyl ester without decomposing the alkyladamantyl ester. The crude alkyladamantyl ester such as crude 2-methyl-2-adamantyl methacrylate is distilled in the presence of a heterocyclic compound and/or a basic compound such as 3-ethyl-3-hydroxymethyloxetane or diglycidyl bisphenol A.

Preparation of crowded olefins from polycycloalkanones via Corey homologative epoxidation by trimethylsulfoxonium iodide/potassium tert-butoxide followed by reaction with lithium dialkylcuprates and thionyl chloride giving the corresponding alkylidenepoly