Allylic rearrangement of trans-pinocarveol esters

The allylic rearrangement of trans-pinocarveol esters ( I ) to myrtenol esters ( II ), a reaction of interest in the chemistry of terpenes and cannabinoids, has been theoretically investigated. The intramolecular, cyclization-induced rearrangement results in equilibrium mixtures of the starting compounds and the products with the ratio of I vs. II in the equilibrium mixture being determined by their thermodynamic stabilities. The relative thermodynamic stabilities as reflected by calculated AM1 heats of formations (ΔHf) were determined for various I-II ester pairs. The study, in agreement with available experimental evidence, indicates that generally I , which contain an endocyclic double bond, are more stable and thus predominantly form following rearrangements. In two cases (acetate and pivalate) the stability is reversed. Calculations performed for similar structures, esters of 2-methylene cyclohexane-1-ol ( IV ) and 1-cyclohexene-1-methanol ( V ) gave similar results. Structural and electronic factors which might influence the stability of these compounds were examined. Interestingly, a correlation between thermodynamic stability and dipole moments was observed. © 1996 John Wiley & Sons, Inc.     

Allylic disulfide rearrangement and desulfurization: mild, electrophile-free thioether formation from thiols

[reaction: see text] Secondary and tertiary allylic 2-pyridyl and 2-benzothiazolyl disulfides react with thiol groups at room temperature to give secondary and tertiary allyl alkyl disulfides. On the addition of a phosphine, a desulfurative sigmatropic rearrangement takes place at room temperature to give thioethers.     

Allylic rearrangement in reactions of acetylenic compounds with allyl and benzyl derivatives of boron

Conclusions The reaction for the addition of crotyl and benzyl derivatives of boron to alkoxyacetylenes proceeds with a rearrangement of the allylic type. On alcoholysis, the vinylboranes that are formed here give derivatives of either the 2-alkoxy-1,4-pentadiene or the-alkoxystyrene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2631–2634, November, 1970.     

Allylic alcohols formation by oxidation of allylic phenyl tellurides. A possible [2,3] sigmatropic rearrangement of allylic telluroxides

Treatment of cinnamyl, 3-methyl-2-butenyl, and 2-cyclohexenyl phenyl tellurides with an oxidizing agent such as H₂O₂, NaIO₄ or t-BuOOH at room temperature under nitrogen affords 1-phenyl-2-propenol, 2-methyl-3-butene-2-ol, and 2-cyclohexenol as a sole or main product respectively in a high yield. The formation of these allylic alcohols can be best explained by assuming a [2,3]-sigmatropic rearrangement of the intermediate allylic telluroxides. These tellurides also react with oxygen, the formation of α.β-unsaturated carbonyl compounds being much increased in this oxidation.     

Ruthenium-Catalyzed Allylic Substitution of Allylic Cyclic Carbonates

Allylic substitution of allylic cyclic carbonates with PhSH or PhOH in the presence of CpRu(PPh₃₎₂Cl (5 mol %) afforded (E)-allylic alcohol and erythro-β-hydroxy thiophenoxide or phenoxide respectively, via external attack of nucleophiles to π-allyl ruthenium complex.     

The Faworskii rearrangement in the formation of 17-methyl steroids : The configuration of C-17 bromides

The configuration of 17-bromo-20-keto pregnanes and the 17-methyletianic esters have been determined. The Faworskii rearrangement of the former to give the latter has been observed to be abnormal. It is suggested that C-17 → C-21 halogen transfer intervenes.     

Optimization of the abnormal Beckmann rearrangement: application to steroid 17-oximes

A novel and practical procedure was developed for the abnormal Beckmann rearrangement of steroid 17-oximes. Treatment of the 17-oximes with TFA/CH(OMe)(3) in boiling THF for 2 h gives the corresponding 13,17-seco alkene nitrile products in unprecedented high yields (70-92%). Since the alkene nitriles can be subsequently converted into 18-norsteroids, this general method provides a highly efficient route to these biologically important compounds and, by extension, to other structurally related natural products.     

Perfluoroalkylsulfonyl fluoride-mediated abnormal Beckmann rearrangement of steroid 17-oximes with acid-labile groups

A perfluoroalkylsulfonyl fluoride-mediated abnormal Beckmann rearrangement is reported which transforms steroid 17-oximes to the corresponding alkene nitriles regioselectively in good yields. This reaction is rapid (completes in 25 min), mild (proceeds at room temperature) and, most importantly, tolerates various acid-labile functional groups, such as methoxymethyl (MOM), ketal, and methyl enol ether, providing access to molecules that would be difficult to synthesize using existing methods.     

5-Bromo- and 5-chloro-3-thiolene-2-one : Allylic rearrangement in 5-bromo-3-thiolene-2-one

5-Bromo- and 5-chloro-3-thiolene-2-one have been prepared by acid-catalysed dealkylation of 5-bromo- and 5-chloro-2-t-butoxythiophene, respectively. On storage in the liquid state at −20°, 5-bromo-3-thiolene-2-one undergoes allylic rearrangement to 3-bromo-3-thiolene-2-one. At room temperature 5-bromo-3-thiolene-2-one rapidly decomposes to a black tar with formation of a mixture of products among which 3-bromo-3-thiolene-2-one, 3-thiolene-2-one, hydrogen bromide, and hydrogen sulphide have been identified. The NMR spectra of 5-bromo- and 5-chloro-3-thiolene-2-one in CCl₄ show that they exist almost exclusively as such, and have been analysed according to the ABX case. From the theoretical spectra it is deduced that J_AX(J₃₄) and J_BX(J₄₅) are of the same sign.     

Sulfinimine-mediated asymmetric synthesis of beta-hydroxy alpha-amino phosphonates

The addition of potassium dialkyl phosphites to enantiopure O-protected alpha-hydroxy sulfinimine pseudoenantiomers affords beta-hydroxy alpha-amino phosphonates in good yield and de. The reaction exhibits a strong match-mismatch effect.     

烯丙位氧化的几种方法

综述了近年来烯丙位氧化的研究进展，详细讨论了过渡金属及其络合物、硒化 合物在烯丙位氧化中的应用，并简述了丁基锂方法、固相催化方法、生物氧化方法 和次氯酸钠氧化方法在烯丙位氧化中的应用．     

Iron‐Catalyzed Allylic Amination Directly from Allylic Alcohols

Allylic amination, directly from alcohols, has been demonstrated without any Lewis acid activators using an efficient and regiospecific molecular iron catalyst. Various amines and alcohols were employed and the reaction proceeded through the oxidation/reduction (redox) pathway. A direct one‐step synthesis of common drugs, such as cinnarizine and nafetifine, was exhibited from cinnamyl alcohol that produced water as side product.     

Allylic lithiation of methylenecyclobutanes

Methylenecyclobutanes undergo a lithiation reaction in the presence of n-BuLi or n-BuLi/KO^tBu from −78 °C to room temperature or to 40 °C in THF within 3 h and then quenching with a variety of electrophiles to give the corresponding addition products (alcohols) in moderate to good yields within 2 h. The alcohols can be easily oxidized to the ketones, which can be transformed to the substituted cyclopentenes in the presence of AlCl₃ within short reaction time.