Complex metal hydrides of aluminum in the presence of cp2ticl2. Hydroalumination versus deprotonation of alkynes with sterically. Aug 01, 2008 the course of hydroalumination and hydrogallation reactions of alkynes depends strongly on the respective conditions such as temperature, solvents, substituents, impurities, etc. As soon as the terminal alkyne is formed, it will be. The addition of the alh bonds to the double or triple bonds of unsaturated organic compounds hydroalumination finds widespread application as a very powerful method for the reduction of specific substrates in organic synthesis 715.
The oshima group have demonstrated using hydroindation with hincl selectively favors z geometry. Alkenylaluminium reagents 1a and 1b, prepared by hydroalumination, were readily converted into the desired coupling. The generality and feasibility of these reactions for both unconjugated alkenes and alkynes, and also for a wide variety of carbonyl and related compounds, were. Tetrahedron letters pergamon tetrahedron letters 43 2002 12311233 cp2ticl2catalyzed hydroalumination of internal alkynes. The addition is cis type, giving rise to z alkenylalanes. The first are obtained by hydroalumination of alkynes with e. A straightforward and efficient method for the synthesis of 1,2diarylsubstituted enamines through the cucatalyzed electrophilic amination reaction of obenzoyl hydroxylamines with vinylaluminum reagents generated in situ from the nicatalyzed hydroalumination of readily accessible internal aryl acetylenes is described. Alkynes are hydrocarbons with carbontocarbon triple bonds and properties much like those of alkenes.
Mechanism of alkene and alkyne hydroalumination with organoaluminium compounds catalyzed by zirconium pcomplexes the thermal hydroalumination of alkenes discovered more than 50 years ago is widely used both in the laboratory practice and in industry. Apr, 2014 hydroalumination iodination of alkyne 1,4diols of different structure showed that with increasing number of substituents at the coh group the amount of. Hydroalumination of alkenes and alkynes request pdf. The use of metal complex catalysts allowed performing this reaction under mild conditions with. Stereoisomerically pure trisubstituted vinylaluminum reagents. Mechanisms of reactions of organoaluminium compounds with.
Hydroalumination of olefins catalyzed by transition metal. Some other functional groups contain nitrogen atoms, such as the amines and amides. The catalytic hydroalumination of 1 alkynes such as 1hexyne and 1octyne with lialfl 4 has been investigated in the presence of ticp 2 cl 2 at 30c. Efficient hydroalumination of terminal alkynes and crosscoupling of the derived alanes philip andrews, a christopher m. The monograph treats the reduction of carbonyles, alkenes, imines and alkynes, as well as reductive aminations and cross and heck couplings, before finishing off with sections on kinetic resolutions and hydrogenolysis.
Alphaselective nicatalyzed hydroalumination of aryl and. Polarity alkynes are slightly more polar than alkenes because sp hybridized carbon is more electronegative in comparison of sp2 hybridized carbon atom of alkenes chemical properties of alkynes 1. Hydroalumination addition of an alh bond and carbalumination addition of an alc bond have been discussed in comc1982 and comc1995. Dec 15, 2009 the hydroalumination of alkynes this edition was published in 1980. Institute of petrochemistry and catalysis of russian academy. Hydroalumination and hydroboration usually proceed by syn fashion, therefore selectively favors e geometry. Number the chain from the end closest to the triple bond. The hydroalumination of alkynes this edition was published in 1980. If an internal alkyne is used, there is not regiochemistry involved and a mixture of e and z isomers is obtained. Reactions of alkenyl and alkynylaluminium compounds involve the transfer of a nucleophilic alkenyl or alkynyl group attached to aluminium to an electrophilic atom. Recent citations interception of elusive cationic hf al and hf zn heterobimetallic adducts with. We assumed that the presence of cp 2zrcl 2 in the reaction mixture could promote the reaction, but the addition of 0. Stereoisomerically pure trisubstituted vinylaluminum.
For example, alkynes undergo many of the typical addition reactions of alkenes. Hydroalumination of alkene s and alkynes with lialh. Stereospecific hydroalumination, carboalumination, and terminal alkyne. Compounds with triple bonds at the end of a molecule are called. Hence, it is difficult to suggest a generally applicable simple scheme for predicting unambiguously the formation of a particular product.
Protodesilylation of the enantiomerically enriched 1,4dienes shown in table 3, obtained from the singlevessel process, can be utilized to access the products expected from a sequence beginning with hydroalumination of arylsubstituted terminal alkynes, which, as mentioned before, undergo hydrometallation inefficiently. Edition notes thesis doctoraluniversity of california, davis, 1968. Reaction of an nal flpbased aluminum hydride toward. Myers hydrozirconation and carbozirconation chem 115. Thf efficient hydroalumination of terminal alkynes and crosscoupling of the derived alanes.
Selective nickelcatalyzed hydroalumination of terminal alkynes full text html pdf. Institute of petrochemistry and catalysis of russian. Hydrohalogenation of alkynes with practice problems. The hydrolysis of the hydroalumination products gave hexane or octane together with 1hexene or 1octene. Ncme2ch22ch2 with several terminal and internal alkynes were studied. Moreover, bis hydroalumination compounds otmpc 6 h 4alcr 1 chr 2 2 r 1,r 2 sihme 2,pph 2 9 and sihph 2,pph 2 10 were produced. The hydroalumination of 1octyne was carried out at 0 o c, treatment of the reaction mixture with hydrochloric acid gave 1octene 87% and n e an ct o 12%. It is one of the major themes within organometallic chemistry. The reagent most often used for this process is diisobutylaluminum hydride dibalh, and this will reduce both terminal. Pdf hydroalumination of alkenes and alkynes with lialh4. The known estereoselective reduction of internal alkynes with lialh4 is reversed in the presence of catalytic amounts of.
Lewis acidcatalyzed trans carbosilylation of simple alkynes yamamoto et al. Hydroalumination of alkenes and alkynes by primary aluminum. Illustrative organoaluminium compounds are the dimer trimethylaluminium, the monomer triisobutylaluminium, and the titaniumaluminium compound called tebbes reagent. The reactions of the sterically crowded primary alane arpri8alh22 arpri8 c6h2,6c6h22,4,6pri323,5pri2 with alkynes and alkenes are described. The generality and feasibility of these reactions for both unconjugated alkenes and alkynes, and also for a wide variety of carbonyl and related. Hydroalumination offers a controlled method to functionalize alkenes and alkynes. Cucatalyzed electrophilic amination of internal alkynes via. Just like for alkenes, antimarkovnikov addition of hydrogen bromide to alkynes can be achieved when the reaction is carried out in the presence of peroxides. Jul 12, 20 the sequential hydroalumination or methylalumination of various alkynes catalyzed by different catalyst systems, such those based on sc, zr, and ni complexes, and the subsequent carboxylation of the resulting alkenylaluminum species with co 2 catalyzed by an n. They suggested that the reaction proceeds by a radical mechanism. Myers hydrozirconation and carbozirconation chem 115 ch 3lizncl 2 reverses the regioselectivity in hydrozirconation of propargylic alcohols.
They predict that hincl adds to alkyne by radical addition in a z geometry. Alkynes are similar to alkenes in both physical and chemical properties. A method for nicatalyzed hydroalumination of terminal alkynes, leading to the formation of alphavinylaluminum isomers efficiently 98% conv in 212 h and with high selectivity 95% to. Mechanisms of reactions of organoaluminium compounds. Regio and stereoselective multisubstituted olefin synthesis. The catalytic hydroalumination of terminal alkynes to alkenes was also described together with reaction of the internal alkynes. Polymerization is minimized with the use of one equiv. Stereospecific hydroalumination, carboalumination, and terminal alkyne metalation are useful methods for generation of the necessary alkenyl and alkyn. Hydroalumination of an alkyne, followed by hydrolysis of the resulting alkenyl aluminum compound, results in overall reduction of the alkyne to an alkene. Latham, marc magre, a darren willcox a and simon woodwarda stabilized alhcl 2 thf 2 hydroaluminates rc. An na radical donates an electron to one of the p bonds in a carboncarbon triple bond. Aug 18, 2010 to initiate our search for an effective alkyne hydroalumination catalyst, we focused on ni complexes, partly based on a report by eisch regarding reactions of a small number of disubstituted alkynes promoted by niacac 2.
The base we will use is nh 2 this is a double elimination. In contrast, the formal analogous addition of ammonia or primary and secondary amines to nonactivated alkenes and alkynes scheme 1. Hydroalumination of alkenes and alkynes by primary. Preparation of alkynes alkynes are prepared by treating vicinal or geminal dihalides with two equivalents of strong base chapter 8.
Some special features of hydroaluminationiodination of. The international union of pure and applied chemistry iupac names for alkynes parallel those of alkenes, except that the family ending is yne rather than ene. Cucatalyzed electrophilic amination of internal alkynes via hydroalumination hongju yoon, yuna kim and yunmi lee department of chemistry, kwangwoon university, seoul 01897, republic korea supporting information general. New insights into the course of wellknown reactions. Alkynes alkynes or acetylenes are compounds that contain a carbon. Irw, regio and stereoselectivity under efficient zrcl. Organoaluminium chemistry is the study of compounds containing bonds between carbon and aluminium. Negishis catalyzed carboalumination with ti and zr 1978. Thus, consistent with literature reports, terminal alkyne. The limitations of the hydroalumination of alkynes, with emphasis on chemo. Pdf cp 2ticl 2catalyzed hydroalumination of internal. The position of the triple bond can alter the reactivity of the alkyne. Ch is a colorless gas that burns in oxygen to form co 2 and h 2o. Selective nicatalyzed hydroalumination of aryl and alkyl.
Hydroalumination of alkenes and alkynes with complex metal hydrides of. Simple alkynes are named much like alkenes, except the ending is changed fromane toyne. Cucatalyzed electrophilic amination of internal alkynes. Latham,a marc magre,a darren willcoxa and simon woodwarda a school of chemistry, the university of nottingham, university park, nottingham, united kingdom. Metal complex catalysis in the synthesis of organoaluminium. The hydroalumination of terminal alkynes, symmetrical and asymmetrical internal alkynes, silyl acetylenes, tin acetylenes, as well as the preparation of e and z vinyl organochalcogens are discussed in detail. A onepot twostep procedure of osilylation followed by hydrosilylation has been developed using tmds. Just like for alkenes, antimarkovnikov addition of hydrogen bromide to alkynes can be achieved when the reaction is. Enantioselective reductive coupling of alkynes and imines. This forms an anion, which can be protonated by a hydrogen in an ammonia solvent. Hydroalumination of olefins catalyzed by transition metal compounds. As part of a program to exploit directing groups in alkyne functionalization reactions,3,4 we explored the hydrozirconation of propargylic alcohols. Efficient hydroalumination of terminal alkynes and crosscoupling of the derived alanes.
Oct 15, 2004 the fact that the hydroalumination of 1. Efficient hydroalumination of terminal alkynes and crosscoupling of. Alkylation of acetylide anions is a general method of making higher alkynes from simpler alkynes. Selective nickelcatalyzed hydroalumination of terminal alkynes full text. Preparation of alkynes by alkylation of acetylene and terminal alkynes acetylide anions are strong nucleophiles and will undergo nucleophilic substitution reactions with primary alkyl halides, resulting in the formation of a cc bond. In contrast, the formal analogous addition of ammonia or primary and secondary amines to nonactivated alkenes and alkynes scheme 1 does not have comparable significance. The amination is catalyzed by 1 mol% cucl without any additive at. It is shown that hydroalumination of the terminal alkynes hccsime3 and hccph readily occurs under mild conditions via the cisaddition of the alh moiety across the cc triple bond with no evidence of hydrogen elimination. The hydroalumination of alkynes 1980 edition open library. Methods for nicatalyzed hydroalumination of terminal alkynes, leading to the.
Alkynes are insoluble in water but readily soluble in nonpolar solvents like benzene, ether etc 4. Hydroalumination of alkene s and alkynes with lialh catalyzed. Many regio and stereoselective modifications of related reactions are known. The known estereoselective reduction of internal alkynes with lialh4 is reversed in the presence of catalytic amounts of cp2 ticl2 producing the zalkenes. The authors propose that alkoxide generation with ch 3li promotes directed hydrometalation, while zncl 2 blocks isomerization to the thermodynamically favored linear vinylzirconium species. Aug 11, 2020 for terminal alkynes the addition of water follows the markovnikov rule, as in the second example below, and the final product ia a methyl ketone except for acetylene, shown in the first example.
For internal alkynes the triplebond is within a longer chain the addition of water is not regioselective. Efficient hydroalumination of terminal alkynes and crosscoupling of the derived alanes philip andrews,a christopher m. Thf efficient hydroalumination of terminal alkynes and crosscoupling of the derived alanes andrews, philip. Alkynes are hydrocarbons with carboncarbon triple bonds. A method for nicatalyzed hydroalumination of terminal alkynes, leading to the formation of. Selective nicatalyzed hydroalumination of aryl and.
Many functional groups contain oxygen atoms, such as alcohols, ethers, aldehydes, ketones, carboxylic acids, and esters. Alkenylaluminium reagents 1a and 1b, prepared by hydroalumination, were readily converted into. Aluminum hydride catalyzed hydroboration of alkynes edinburgh. If you are making a terminal alkyne, you need 3 equivalents of nh 2 why. Stereospecific hydroalumination, carboalumination, and terminal alkyne metalation are useful methods for generation of the necessary alkenyl and alkynylalanes. Natural bond orbital nbo analysis was performed, which revealed the inequivalent charge distribution on the c c carbon atoms of the alkynes that have two. The combustion of acetylene releases more energy per mole of product formed than any other hydrocarbons. When the silane hydride is tethered to the alkyne via osilylation, 6 and 7membered endocyclic vinyl siloxanes are formed exclusively.
A method for nicatalyzed hydroalumination of terminal alkynes, leading to the formation of alphavinylaluminum isomers efficiently 98% conv in 212 h and with high selectivity 95% to 98%. With its comprehensive overview of modern reduction methods, this book features high quality contributions allowing readers to find reliable solutions quickly and easily. A straightforward and efficient method for the synthesis of 1,2diarylsubstituted enamines through the cucatalyzed electrophilic amination reaction of obenzoyl hydroxylamines with vinylaluminum reagents generated in situ from the nicatalyzed hydroalumination of readily accessible internal aryl acetylenes. Alkynes can be reduced to transalkenes with the use of sodium dissolved in an ammonia solvent. In the case of symmetric secondary 1,4diols the reaction results in a 1.
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