Structure ofliquids / Liquid association / Hydrogen-bonding / Nuclear magnetic relaxationProton relaxation rates 1/7*, of methyl protons and hydroxyl protons have been measured in the system methanol -CC14 at 298 K. By means of the association parameter A, self-association relative to the hydroxyl group and the methyl group of methanol was found. Closest distances of approach between OH-and CH3-protons of methanol and configurations of maximum occurrence probability are reported. For the pure liquid methanol a comparison of our results with X-ray, neutron-diffraction and computer simultation data is given.Am System Methanol-CCl4 wurden Protonen-Relaxationsraten l/7\ fur die HydroxylProtonen und die Methyl-Protonen bei 298 K gemessen. Mit Hilfe des sogenannten /(-Parameters wurde Selbstassoziation beziiglich der Hydroxyl-und der Methyl-Gruppe von Methanol gefunden. Dichteste intermolekulare Annaherungsabstande zwischen OH-und CH3-Protonen von Methanol und Molekiilpaarkonfigurationen maximaler Wahrscheinlichkeit werden angegeben. Fur die reine Fliissigkeit werden die Ergebnisse dieser Untersuchung mit Rontgen-und Neutronenstreudaten sowie mit Ergebnissen aus einer Computer-Simulation verglichen.

Efficient Pd-catalyzed cyclization of homoallylated bbromo-vinylalcohols via a domino process to carbocycle derivatives in presence of different bases is reported. An unexpected and novel palladium-mediated Heck-type intramolecular oxidative cyclization of 1-bromohexa-1-ene-5-yn-3-ol derivatives is also described.The formation of carbon-carbon bonds using in situ generated organometallic reagents is of fundamental importance in organic synthesis. 1 Palladium catalysts have emerged as extremely powerful tools for the construction of carbon-carbon bonds. 2 Their popularity stems in part from their capability to oxidize, 3a,b reduce, 3c,d isomerize 3e,f as well as to form new bonds. Substituted carbocycles represent a common structural component of naturally occurring and biologically active molecules. 4 The cyclization of unsaturated substrates using an intramolecular Heck reaction promoted by organopalladium complexes is of fundamental importance for the construction of a vast array of mono-and polycarbocyclic and also polyheterocyclic systems 5 and is therefore a highly attractive feature in the synthesis of cyclic natural products. 5e In this context, we have recently reported 6 a new palladium-promoted domino C-C cyclopalladation sequence allowing the facile one-pot synthesis to cyclopentenones with promising synthetic value. The 1-bromohexa-1,5-diene-3-ol derivatives underwent Pd-catalyzed oxidative cyclization to functionalized cyclopentenones in very good yields. In this communication we wish to report the reactivity of new sensitive substrates towards palladium-catalyzed intramolecular Heck reaction, which provides an efficient route to cyclopentenones and cyclohexenones.The starting materials were synthesized by addition of the Grignard reagents derived from 4-bromo-1-butene and Mg to bromoaldehydes (Scheme 1) in tetrahydrofuran (THF) to afford bromo alcohols (1a-6a, Table 1) in good yield.Applying Heck reaction to the compounds 1a-6a under standard conditions, 7 produced substituted cyclohexenones (Scheme 2) exclusively through 6-exo-trig cyclization pathways. Scheme 2In our previous communication, we opted for HCOONa as the base, but later, we performed the reaction with other bases (Na 2 CO 3 , K 2 CO 3 , NaOAc, Et 3 N) and acetonitrile as solvent. In all these cases we successfully isolated the cyclized products. To improve the yield further, we incorporated tetrabutyl ammonium chloride as additive, which was found to be effective in all cases ( Table 2).The structure of 6b was unambiguously determined by Xray crystallographic analysis (Figure 1). Figure 1 ORTEP view of the structure 6bAs we could not isolate any intermediate for this reaction, we speculate that the mechanism follows the sequence in Scheme 3. During the search for an intermediate, we synthesized compound I by O-alkylation of 1-(2-bromoBr H OH Pd(OAc) 2 / PPh 3 DMF or MeCN O TBAC bases Scheme 1 Br CHO THF, -78 °C to 0 °C Br H OH Mg, 4-bromo-1-butene Downloaded by: UC Santa Barbara. Copyrighted material. 2136 D. Ray et al. LETTER Synlett...

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