30656-45-2Relevant articles and documents
On the regioselectivity of Pd-catalyzed additions of organoboronic acids to unsymmetrical alkynes
Kim, Nakjoon,Kim, Ki Seong,Gupta, Aruna Kumar,Oh, Chang Ho
, p. 618 - 619 (2004)
The Pd-catalyzed reaction of unsymmetrical alkynes 1 with organoboronic acids 2 gave a mixture of products 3 and 4, whose ratios were controlled by the electronic as well as steric effects of the substrates 1.
Formation of a manganese alkyl complex as an intermediate in the ring-opening hydroformylation of α-cyclopropylstyrene by HMn(CO)5
Bullock, R. Morris,Rappoli, Brian J.
, p. 345 - 368 (2007/10/02)
The reaction of α-cyclopropylstyrene (CPS) with HMn(CO)5 can result in either hydrogenation or hydroformylation.The hydrogenation occurs by a previously established pathway involving sequential hydrogen atom transfers from the metal hydride to the organic substrate, and is the predominant reaction observed with samples of HMn(CO)5 that have been thoroughly dried and purified using P2O5.With samples of HMn(CO)5 that have been not been treated with P2O5, the reaction that occurs with CPS is ring-opening hydroformylation, leading to the isolation of Mn2(CO)9(η1-HCOCH2CH2CH=C(Ph)CH3).The detailed procedures for preparation and handling of HMn(CO)5 that are reported in this paper enable the hydroformylation reaction to be reproducibly observed as the predominant reaction.An induction period of a few hours is typically observed in the hydroformylation, but addition of Mn2(CO)9(η1-tolualdehyde) eliminates the induction period.The hydroformylation reaction is inhibited by CO (1 atm).The manganese alkyl complex (CO)5MnCH2CH2CH=(Ph)CH3 is an intermediate in the hydroformylation.The details of the mechanism of formation of this alkyl complex from CPS and HMn(CO)5 are not completely understood, but several mechanistic possibilities are considered.
β-Halogeno Ether Synthesis of Olefinic Alcohols: Stereochemistry of the Ring-scission of 2-Substituted 3-Halogenotetrahydro-pyrans and -furans
Crombie, Leslie,Wyvill, Robert D.
, p. 1983 - 1996 (2007/10/02)
The stereochemical outcome of the sodium ring-scission of 2-substituted 3-halogenotetrahydro-pyrans and -furans, with 2-substitution represented by alkyl, alkenyl or aryl, is presented.Although the cis- and the trans-tetrahydropyran scissions are hyghly stereoselective for (E)-5-substituted pent-4-enol, this stereoselectivity breaks down when the 2-substituent is conformationally undiscriminating (deuterium) or has substantial anomeric effects (methoxy).Consideration of this, along with conformational data from the preceding paper, provides an explanation of the stereoselectivity of the tetrahydropyran scission.Evidence against a radical, and for a carbanion intermediate is presented and a common, very rapidly inverting, 3-carbanion is considered to be formed from either cis- or trans-stereoisomers.Ring scission is also rapid (the carbanion cannot be trapped), but less rapid than carbanion inversion, and takes place before the slower conformational inversion can occur so that the (E)/(Z)-nature of the unsaturated alcohol produced is controlled by the initial tetrahydropyran conformation.The unstereospecific nature of the ring scission of both cis- and trans-2-alkyl-3-chlorotetrahydrofurans is explained as a consequence of their existence in conformational equilibria. The high stereoselectivity of the ring scission of cis- and trans-3-chloro-2,3-dimethyltetrahydropyrans, and the poor stereoselectivity of the scission of 2-alkyl-3-chloro-2-methyltetrahydrpyrans, is explained; the reaction of sodium with 2-butyl-3,3-dichlorotetrahydropyran is considered.Using the ring-scission of 3-chlor-2-ethyltetrahydropyran, short syntheses of (+/-)-endo-brevicomin are described to illustrate the utility of β-halogen ether synthesis.
