Stereoselective Radical Addition Research Articles

Origins of stereoselectivity in radical additions: reactions of alkenes and radicals bearing oxazolidine and thiazolidine amide groups

Single-crystal X-ray analysis of four alkenes that undergo stereoselective radical addition reactions are reported. The facial selectivity of radical additions to these alkenes is understood based upon their solid-state conformations. Alkenes which have a conformation placing a group at a position in space sterically protecting one the faces from addition undergo radical addition with diastereofacial selectivity. The structures of the alkenes are analyzed by the polar coordinates of groups relative to the alkenes center undergoing addition

Radical addition to vinylphosphine oxides: 1,2-stereoinduction of phosphorus stercogcnic centre

Carbon cantered radicals derived from reactions of halides 3–5 with Bu3SnH in the presence of AIBN havebeentrapped by diphenylvinylphosphine oxide 2 giving the addition products 6–8 in high yields. Free radical addition to 2 employing the Barton methodology gave lower yields. The use of chiral (racemic:) vinylphosphine oxides allowed a stereoselective radical addition with a diastercomeric ratio as high as 9:1 for mesitylmethylvinylphosphine oxide 1.

ChemInform Abstract: α‐Sulfinyl‐Substituted Radicals. Part 1. Stereoselective Radical Addition Reactions of Cyclic α‐Sulfinyl Radicals.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

α-Sulfinyl Substituted Radicals; I. Stereoselective Radical Addition Reactions of Cyclic α-Sulfinyl Radicals1

α-Sulfinyl Substituted Radicals; I. Stereoselective Radical Addition Reactions of Cyclic α-Sulfinyl Radicals¹

ChemInform Abstract: Highly Stereoselective Radical Addition to a Trisubstituted Alkene by Low Temperature Photolysis of Thiohydroxamic Esters.

AbstractThe α,β‐unsaturated chiral amide (VIII), prepared as shown in the reaction scheme, is alkylated with the organomercury halides (IX) to give predominantly the (S,S,S)‐diastereomers (X).

ChemInform Abstract: Et3B‐Induced Stereoselective Radical Addition of Ph3GeH to Carbon‐Carbon Multiple Bonds and Its Application to Isomerization of Olefins.

AbstractThe isomeric ratios of the products depend on the reaction time, solvent and the ratio acetylene: Ph3GeH.

Et3B Induced Stereoselective Radical Addition of Ph3GeH to Carbon–Carbon Multiple Bonds and Its Application to Isomerization of Olefins

Abstract Triphenylgermane easily adds to acetylenes or terminal olefins in the presence of Et3B to give alkenyltriphenylgermane or alkyltriphenylgermane respectively under excellent control of regio- and stereoselectivities. While Et3B catalyzed addition of Ph3GeH to 1-dodecyne at −78 °C affords (Z)-1-triphenygermyl-1-dodecene exclusively, the addition of Ph3GeH at 60 °C provides (E)-1-triphenylgermyl-1-dodecene as a single product. The triphenylgermyl radical is also effective to isomerize Z-olefins into their thermodynamically more stable E-isomers.

ChemInform Abstract: Triethylborane‐Induced Stereoselective Radical Addition of Perfluoroalkyl Iodides to Acetylenes.

AbstractThe alkynes (I) react with the perfluoroalkyl iodides (II) in the presence of triethylboron to form exclusively the iodo olefines (III) bearing the iodide and the perfluoroalkyl substituent in trans‐position.

Highly stereoselective radical addition to a trisubstituted alkene by low temperature photolysis of thiohydroxamic esters

Low temperature carbon radical addition to α,β-unsaturated amides of trans-2,5-dimethylpyrrolidine was achieved in high yield with high diastereoselectivity by photolysis of Barton esters. Use of an olefin substituted with three electron withdrawing groups provides synthetic versatility and regiospecificity.

新規ラジカル発生法とその有機合成への応用 Ｒ３ＳｎＨ‐Ｅｔ３Ｂ系によるラジカル反応

Synthetically useful radical reactions mediated by Et3B are described. An addition of catalytic amount of Et3B to a solution of triphenylstannane, triphenylgermane, or benzenethiol in toluene promotes the effective formation of the corresponding triphenylstannyl, triphenylgermyl, or benzenethiyl radical, respectively. Topics are (1) Et3B induced radical addition of R3SnH to acetylenes and its application to cyclization reaction, (2) Et3B induced stereoselective radical addition of Ph3GeH to acetylenes and its application to isomerization of olefins, (3) Et3B induced radical addition of thiols to acetylenes, (4) A facile reduction of dithiocarbonates with n-Bu3SnH-Et3B, (5) Et3B induced hydrodehalogenation of organic halides by tin hydrides, and (6) Et3B-mediated Reformatsky type reaction and three component coupling reaction of alkyl iodides, methyl vinyl ketone, and carbonyl compounds.

Triethylborane-induced stereoselective radical addition of perfluoroalkyl iodides to acetylenes

Treatment of terminal or internal acetylenes bearing a variety of substituents with perfluoroalkyl iodides in the presence of a catalytic amount of triethylborane provides the corresponding perfluoroalkenes in good to excellent yields. The addition of perfluoroalkyl iodides to olefins is also described.

ChemInform Abstract: Et3B-Induced Stereoselective Radical Addition of Ph3GeH to Acetylenes and Its Application to Isomerization of Olefins.

The acetylenes (I) are coupled with triphenylgermane (II) in the presence of triethylboron to give the alkenylgermanes (III).

Et 3B induced stereoselective radical addition of Ph 3GeH to acetylenes and its application to isomerization of olefins

Triphenylgermane adds easily to acetylenes in the presence of Et 3B to give (E)- or (Z)-alkenyltriphenylgermanes, respectively, under excellent control of regio- and stereoselectivities.