Alkynes reactions with alkenes

Ethyl 4.4,4-trifluorobut-2-ynoate reacts with various dienes (Table 3). " With a iionsymmctric diene, the cycloadduct is obtained as a mixture of regioisomers. This suggests that, unlike reactions with alkenes, reactions with alkynes arc not governed by the ester substituent. Cycloadducts can also undergo a further cycloaddition, in particular when the diene is used in excess. 

Anhydro-3-hydroxy-2-phenylthiazolo[2,3-6]thiazolylium hydroxide (407) underwent ready thermal reaction with alkynic and alkenic dipolarophiles in refluxing toluene. With the former dipolarophile sulfur was lost from the intermediate 1 1 cycloadduct (408) to give the substituted 5H-thiazolo[3,2- i]pyridin-5-ones (409). With the latter, the intermediate (410) lost H2S, also forming (409). 

Chirality center, 292 detection of, 292-293 Eischer projections and, 975-978 R,S configuration of, 297-300 Chitin, structure of, 1002 Chloral hydrate, structure of, 707 Chloramphenicol, structure of, 304 Chlorine, reaction with alkanes, 91-92,335-338 reaction with alkenes, 215-218 reaction with alkynes, 262-263 reaction with aromatic compounds, 550 Chloro group, directing effect of, 567-568... 

Introduction of two different chalcogen elements to the C-C unsaturated bond is of particular interest from both synthetic and mechanistic viewpoints. Therefore, extensive studies have been carried out on the development of the (RE)2/(R E )2 binary system without using RE-E R compounds, which are difficult to prepare. (Z)-l-Seleno-2-thio-1-alkenes are produced regio- and stereoselectively when a mixture of diaryl disulfides and diaryl diselenides is subjected to a rhodium-catalyzed reaction with alkynes (Equation (68)).193... 

The highly reactive nature of (P)Rh is perhaps best demonstrated by the reaction of electrochemically generated (TPP)Rh with terminal alkenes and alkynes. The overall reaction with alkynes is given by Equation 7 and the suggested mechanism... 

Electron-rich 3-methoxy-4-trimethylsilyl-l,2-butadiene (22) reacted with several electron-poor alkenes in the presence of diethylaluminum chloride to afford methylene cyclobutanes 23. Reactions with alkynes were performed in the presence of methylalu-minum bis(2,4,6-tri-t-butylphenoxide) (equation 7)16. 

Hull MW, Sevov SC (2007) Addition of alkenes to deltahedral zintl clusters by reaction with alkynes synthesis and stmcture of [Fc-CH=CH-Ge9CH-Fc] an organo-zinti-organometal-lic anion. Angew Chem Int Ed 46 6695-6698... 

The triphenyl derivative (91, R = R = R = Ph, R = H) is formed in a mechanistically interesting reaction between benzoyl formic acid anil (Ph-N=CPh-C02H), trifluoroacetic anhydride, and pyridine. Its 1,3-dipolar cycloaddition reactions with alkynes and alkenes have been reported. ... 

Secondary thioamides, precursors of N-protonated azomethine ylids, give A1-pyrrol ine derivatives (after elimination of thiol). When the dipolarophiles are dissymmetric alkenes, high regioselectivity is obtained. Reaction with alkynes leads to pyrrole derivatives in good to excellent yields and with ArCHO leads regioselectively to 2,5-disubstituted 2-oxazolidines in moderate yields.264... 

The intramolecular Alder-ene reaction (enyne cydoisomerization reaction) with alkynes as the enophiles has found wide application compared with diene systems. The reason may be the ready chemo-differentiation between alkene and alkyne functionality and the more reactive alkyne moiety. Furthermore, the diene nature of the products will promote further applications such as Diels-Alder reactions in organic synthesis. Over the past two decades the transition metal-catalyzed Alder-ene cycloisomerization of l,n-enynes (typically n= 6, 7) has emerged as a very powerful method for constructing complicated carbo- or heterocydic frameworks. The transition metals for this transformation indude Pd, Pt, Co, Ru, Ni-Cr, and Rh. Lewis acid-promoted cydoisomerization of activated enynes has also been reported [11],... 

Hydroxy(tosyloxy)iodo]benzene and Its Analogues Reactionswith Alkenes and Allenes. Reactions with Alkynes and Alcohols. Reactions with Keto Compounds. Reactions with Nitrogen, Sulfur, and Other compounds. 

Phosphonoacrolein, (Et0)2P(0)C(CH0)=CH2, takes part in hDA reactions with alkenes and cyclic conjugated dienes, to give phosphono-substituted 3,4-dihydro-2W-pyrans and their annulated derivatives. The reaction with alkynes gives the 1 1 adduct, a 4//-pyran, initially but this undergoes a second cycloaddition leading to a tetrahydropyrano[3,2-6]pyran 3... 

The Lewis acid-catalyzed reactions of allylsilanes with simple alkenes and alkynes introduce both allyl and silyl groups into the unsaturated bonds (Equations (53) and (54)).209 210b These allylsilylations are 7-regiospecific with respect to allylsilanes. The /raor-addition of allylsilanes occurs in the reaction with alkynes. There are two possible mechanisms for the Lewis acid-promoted allylsilylations, that is, trimethylsilyl cation- and Lewis acid-mediated pathways. 

The general characteristics of the reactions of nitrile oxides with alkenes resemble those of the reactions with alkynes.59 The main differences are (i) that there is no evidence for a two-stage mechanism (1,3-addition followed by cyclization) and (ii) that although they are generally regioselective, they are not always markedly so. A further characteristic is that they are stereospecific with respect to the alkene, whose geometry is preserved in the product. 

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