Stereoselective cross-coupling reaction of 1,1-Diboryl-1-alkenes with electrophiles: a highly stereocontrolled approach to 1,1,2-triaryl-1-alkenes

Palladium-catalyzed cross-coupling reaction of 1,1-diboryl-1-alkenes with aryl and alkenyl iodides was found to proceed stereoselectively, giving rise to the corresponding mono-coupled product as a single diastereomer with E-configuration. Second coupling of the initial product with another aryl iodide affords diverse triarylalkenes in their stereochemically pure form. This highly stereoselective approach for triarylalkenes allows one to synthesize both diastereomers in one pot from 1,1-diboryl-1-alkenes.     

A new synthesis of trifluorinated compounds via 1,1-dichloro-1-alkenes in superacid

A two step process for converting ketone or aldehyde via 1,1-dichloro-1-alkenes to the corresponding 1,1,1-trifluoroderivatives is described, based on HF addition and chlorine-fluorine exchange under superacidic conditions.     

Palladium-catalyzed cross-coupling reactions of B-alkyl-9-BBN or trialkylboranes with aryl and 1-alkenyl halides

The reactions of trialkylboranes or B-alkyl-9-BBN with aryl and 1-alkenyl halides take place readily in the presence of PdCl₂(dppf) and sodium hydroxide or methoxide to afford alkylated arenes and alkenes in excellent yields.     

1,1-二卤代-1-烯烃的制备及其在有机合成中的应用

1,1-二卤代-1-烯烃是有机化学中常见的合成片断,在合成化学中已得到了广泛的应用。该综述介绍了这一类化合物常见的制备方法以及反应的适用范围,并详细讨论了该类化合物在有机合成中的应用：(1)1,1-二卤代-1-烯烃在镁、有机锂、锌/溴化亚铜、二碘化钐、零价钯等金属或金属试剂作用下,发生α-消除反应生成烯基卡宾中间体的反应;(2)1,1-二卤代-1-烯烃在合成杂环以及核苷类似物等方面的应用。对于这类化合物在钯催化下的分子内(间)的偶联反应以及利用分子内的双环碳钯化反应,合成环状化合物等等方面的研究进展,也进行了详细的讨论。     

Reaction of 1,1-dichloro-1-nitrosoalkanes with trimethylchlorosilane and zinc

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, p. 745, March, 1989.     

Suzuki reactions of extended scope: the '9-MeO-9-BBN variant' as a complementary format for cross-coupling

While the Suzuki coupling has gained paramount importance, the basic set-up of the reaction has remained essentially unchanged for decades. It consists of the palladium-catalyzed coupling of organoboron reagents with aryl- or alkenyl halides, -sulfonates or related electrophiles in the presence of a base. One of the few alternative formats for this transformation is the '9-MeO-9-BBN variant', which is distinguished by not requiring an added base as a promoter. Rather, polar organometallic reagents R-M (R = Me, alkyl, aryl, heteroaryl, alkenyl, alkynyl etc.) are first intercepted with 9-MeO-9-BBN to give the corresponding borinate complexes, which then pass the R-group onto an organopalladium complex generated in situ as the electrophilic partner. This procedure allowed the structural reach of the Suzuki coupling to be extended, and served in a host of advanced applications, most notably for elaborate sp-sp(2) and sp(3)-sp(2) coupling processes.     

Reaction of 1,1-dichloro-1-nitrosoalkanes with acid chlorides and zinc

1,1-Dichloro-1-nitrosoalkanes, similar to -halocarbonyl compounds, react with acid chlorides and zinc to give O- acylated acylhydroximoyl chlorides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 477–478, February, 1990     

Reaction of 1,1-dichloro-1-nitrosoalkanes with trivalent phosphorus acid chlorides

Conclusions 1,1-Dichloro-1-nitrosoalkanes react with trivalent phosphorus acid chlorides not containing a P-O ether bond in the presence of nucleophilic reagents (sulfur dioxide, ethanethiol) to produce phosphorylated alkylchloroformoximes. This is rationalized in terms of intermediate O-alkylchloroformiminoyldichlorophosphorane formation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya., No. 9, pp. 2128–2132, September, 1988.     

Stereospecific epoxide-opening reactions of 1,1-dibromo-3,4-epoxy-1-alkenes with carbon nucleophiles

The stereospecific epoxide-opening reactions of 1,1-dibromo-3,4-epoxy-1-alkenes with allyltributylstannane and with ketene silyl acetals in the presence of a Lewis acid are described. Both the reactions occurred regioselectively at the allylic position via an S_N2 process giving rise to a single product, respectively. Treatment of the products by the latter reaction with p-TsOH afforded various 3,4-anti- and 3,4-syn-disubstituted γ-lactones in a highly stereoselective manner and high yields.     

The palladium-catalyzed “head-to-tail” cross-coupling reaction of 1-alkenylboranes with phenyl or 1-alkenyl iodides. A novel synthesis of 2-phenyl-1-alkenes or 2-alkyl-1,3-alkadienes via organoboranes

The reaction of phenyl or 1-alkenyl iodides with 1-alkenyl-1,3,2-benzodioxaboroles readily obtainable via the hydroboration of 1-alkynes, gives the corresponding “head-to-tail” cross-coupling products, 2-phenyl-1-alkenes or 2-alkyl-1,3-alkadienes, in good yields. The reaction is effectively catalyzed by catalytic amounts of palladium compounds in the presence of triethylamine.     

Synthesis of carba-analogues of myoseverin by regioselective cross-coupling reactions of 2,6-dichloro-9-isopropylpurine

A series of 9-isopropylpurine derivatives bearing 4-methoxyphenyl, 4-methoxybenzyl, (4-methoxyphenyl)ethynyl and 2-(4-methoxyphenyl)ethyl groups in positions 2 and 6 were prepared as carba-analogues of antimitotic myoseverin. Cross-coupling reactions of 2,6-dichloro-9-isopropylpurine (1) with one equivalent of (4-methoxyphenyl)boronic acid or (4-methoxybenzyl)zinc chloride gave regioselectively the 6-substituted 2-chloropurines which were used for another cross-coupling reaction with a second equivalent of the organometallic reagent. The Sonogashira reaction of 1 with 4-(methoxyphenyl)ethyne gave 2,6-bis[(4-methoxyphenyl)ethynyl]-9-isopropylpurine that was hydrogenated to 2,6-bis[2-(4-methoxyphenyl)ethyl]-9-isopropylpurine. Regioselectivity of the couplings was proved by means of ¹H-¹⁵N HMBC experiments. 2,6-Bis[(4-methoxyphenyl)ethynyl]-9-isopropylpurine showed considerable cytostatic activity, while the other compounds were inactive.     

Nucleophilic substitution in 1-alkyl-4,5-dichloro-3-nitropyridazin-6-ones

Treatment of 1-alkyl-4,5-dichloro-3-nitropyridazin-6-one with C-nucleophiles and with ambident nucleophiles (2-azahetarylacetonitriles) leads to a selective substitution of a chorine atom by the quaternary carbon atom of the carbanion formed from a substituted acetonitrile. The pK_a of the CH-acid 2-(1-alkyl-5-chloro-3-nitro-6-oxo-1,6-dihydro-4-pyridazinyl)malononitrile was determined by potentiometric titration. Reaction of 2-(1-alkyl-5-chloro-3-nitro-6-oxo-1,6-dihydro-4-pyridazinyl)-2-hetarylacetonitriles with primary amines gives 6,7-dihydro-1H-pyrrolo[2,3-d]pyridazin-7-ones. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 556–564, April, 2006.