Lewis acidpromoted allylation with allyltriorganosilanes, the hosomisakurai reaction. The sakurai annulation has proven to be particularly powerfulwhen carried out in tandem with intramolecular aldol or mannich reactions to form complexfused ring systems. Total synthesis of dehaloperophoramidine using a highly diastereoselective hosomisakurai. The catalyst turnover was increased by addition of 1 equiv of meoh. In organic chemistry, the keck asymmetric allylation is a chemical reaction that involves the nucleophilic addition of an allyl group to an aldehyde. Hosomisakurai reaction an overview sciencedirect topics.
Disclaimer the information provided in this channel are subject to your own responsibility, this channel doesnt give any guarantee that the. The fivemembered ring was constructed by the hosomisakurai reaction of the allylsilane derived from the ketone. Intramolecular sakurai condensation tetrahydropyran rings dihydropyrans. Total synthesis of dehaloperophoramidine using a highly diastereoselective hosomisakurai reaction ross. A novel reductive variant of the classical hosomisakurai reaction is reported. A stereoselective reductive hosomisakurai reaction organic letters 2018, 20, 14611464. Asymmetric, antiselective scandiumcatalyzed sakurai. A novel reductive variant of the classical hosomi sakurai reaction is reported. Feb 14, 20 counteranion control enables the enantioselective, organo lewis acid catalyzed hosomisakurai reaction of heteroaromatic aldehydes and allylsilanes using an easily handled disulfonimide precatalyst see scheme. Wikipedia sakurai reaction wikipedia hosomi sakurai reaction. Employing 1 mol% calcium, allylated isoindolinones can be synthesised in high yields and the reaction is shown to be tolerant to a range of medicinally relevant functional groups including heterocycles. Download fulltext pdf total synthesis of dehaloperophoramidine using a highly diastereoselective hosomisakurai reaction article pdf available in chemical communications 5271 august 2016.
The modified sakurai and related reactions multicomponent. A significaant improvement of the reactivity was observed by using thf as the solvent. A rapid and functionally tolerant calcium catalysed hosomisakurai reaction has been realised. Hitomi sakurai, asian maid, pleases master with sex more at. Pdf ebook download opening and bringing to light of a book so long withheld from the gaze of the curious, and even. The sequence employs the newly developed reagent, 41,3dithian2yl2butenyltrimethylsilane 6, which serves as an annulating agent by a combination of michael addition and intramolecular hosomisakurai reaction. Among these methods, the hosomisakurai reaction is promising, since it employs inexpensive. The key to the success of this system is to turn the usually undesired silylium ion catalysis into the desired catalytic regime and pair the cation with an enantiopure. Asymmetric counteraniondirected lewis acid organocatalysis.
The allylsilane will add to the carbonyl compound directly if the electrophile carbonyl group is not part of an. The chirality of the catalyst induces a stereoselective addition, so the secondary alcohol of the product has a predictable absolute stereochemistry based on. This synthesis can be considered a formal synthesis of deoxopinguisone. Thi left lee free to toncentrclte on the quetton of reidnon with the l nued the singapore story memoirs of lee kuan yew pdf free download. Sakurai reaction of allylsilanes containing arabinose. Highly efficient hosomisakurai reaction of aromatic aldehydes. The key to the success of this system is to turn the usually undesired silylium ion catalysis into the desired catalytic regime. The key to the success of this system is to turn the usually undesired silylium ion catalysis into the desired catalytic regime and pair the cation. Applications of iridiumcatalyzed isomerization claisen. All structured data from the file and property namespaces is available under the creative commons cc0 license. Good generality was demonstrated as both aliphatic and aromatic allylsilanes are effective nucleophiles in additions to the glyoxamide 2. Sakurai reaction of allylsilanes containing arabinosederived alcohols as chiral auxiliaries. The iridiumcatalyzed isomerization claisen rearrangement icr methodology developed in thenelson group has provided access to a broad range of diastereomerically enricheddisubstituted unsaturated aldehydes.
Stereochemical studies of agcatalyzed hosomisakurai reaction. The keck asymmetric allylation has many applications to the synthesis of natural products, including. View the article pdf and any associated supplements and figures for a period of 48 hours. Mechanism, references and reaction samples of the hosomisakurai reaction. Wikipedia sakurai reaction wikipedia hosomisakurai reaction. Here, the authors report a catalyst capable of carrying out this reaction on. A catalytic enantioselective hosomisakurai reaction of. An efficient route to the highly functionalized pinane unit present in paeniflorin 1 is described. Request pdf highly efficient hosomisakurai reaction of aromatic aldehydes catalyzed by montmorillonite doped with simple bismuthiii salts.
The first five steps were carried out on seventy gram scale without. Allylsilyl aldehydes produced by the icr reaction havebeen further elaborated into substrates for highly diastereoselective intramolecular. As displayed in the mechanism, the hosomisakurai reaction goes through a secondary. Sakurai and hosomi had previously noted the coupling of allylsilanes to aldehydes in the presence of ticl 4. The sakurai reaction is the chemical reaction of carbon electrophiles with allylic silanes. Request pdf sakurai allylation reaction hosomi sakurai reaction lewis acidmediated addition of allylsilanes to carbon nucleophiles. Experimental procedures and characterization data for all new compounds pdf. It is named after the chemists akira hosomi and hideki sakurai.
Pdf free the successfu1 entry into nanonhood is pnmanly the story of lee kuan yews mslght iii. The complex of agf and rdifluorphos has been shown to be an effective catalyst for the asymmetric sakurai. This transformation hinges on a redoxneutral, stereoselective internal reduction event under mild conditions. Hofmannloffler reaction, lofflerfreytag reaction, hofmannlofflerfreytag reaction. A onepot synthesis of 2,3,5trisubstituted tetrahydrofurans by a double sakuraihosomi reaction was reported and an example is shown below. The key steps included a 3,3claisen rearrangement and an epoxide openingallylsilylation modified hosomisakurai reaction to install the contiguous allcarbon quaternary stereocentres with the required relative stereochemistry. Furthermore, experimental evidences also supported the fluoridetriggered autocatalytic mechanism of the sakurai. Remarkably, among several possible diastereomers only two are generated with high levels of diastereo.
Activation by lewis acids is critical for an efficient allylation to take place. The hosomisakurai reaction on the same substrate 1, on the other hand, yielded a pair of diastereomeric products, 9a and 9b, inseparable by chromatography. Chemistry carbonyl group carbonyl compound detailed mechanism. Allylsilanes are less toxic than allylstannanes and more stable than allyl grignard and allyl lithium reagents.
Pdf total synthesis of dehaloperophoramidine using a. Ria sakurai is close to a massive threesome porn show. Hosomisakurai reaction,11 has been used in natural product synthesis,12 but to the best of our knowledge has not been used in the construction of contiguous allcarbon quaternary centres. The fivemembered ring was constructed by the hosomi sakurai reaction of the allylsilane derived from the ketone.
Allylsilyl aldehydes produced by the icr reaction havebeen further elaborated into substrates for highly diastereoselective intramolecular hosomi sakurai annulation reactions. Based on the crucial importance of allylation reaction, the new developments of hosomisakurai reaction, which could not be ignored in allylation reaction, are summarized involving the catalyst, the electrophiles and the corresponding mechanisms. Lewis acids and fluoride salts are used to promote the reaction. Functionalisation of isoindolinones via a calcium catalysed. Misato sakurai fingers and toys her tits and pussy. This operationally simple reaction relies on readily available starting materials and leads to useful products in diastereoselectivities of up to 7. General characteristics the allylation reactions using allylsilanes are known as the hosomisakurai allylation. Allylation of imines with allyltrimethylsilane and experimental. Aug 17, 2016 the reaction was quenched with 2% vv trifluoroacetic acid in ch 2 cl 2 0. Lewis acidmediated addition of allylsilanes to carbon nucleophiles. Hosomisakurai reactions of silacyclic allyl silanes. A number of lewis acids have so far been found to accomplish the. Pdf total synthesis of dehaloperophoramidine using a highly. The pioneering works by hosomi and sakurai described that conventional lewis acids ticl 4, sncl 4, and bf 3 oet 2 are effective in the allylation of aldehydes, ketones, and acetals with a substoichiometric quantity.
Reaction names can also simply describe the reaction type, often by using the initials or referring to structural features. Hosomisakurai reaction, but boron reagents and others have also been successfully employed. Hosomisakurai reactions of silacyclic allyl silanes chemical. The hosomisakurai allylation and a mukaiyama aldol reaction. Asymmetric synthesis of homoallyl alcohols, using binols 9. The key steps included a 3,3claisen rearrangement and an epoxide openingallylsilylation modified hosomi sakurai reaction to install the contiguous allcarbon quaternary stereocentres with the required relative stereochemistry. The hosomi sakurai reaction involves the lewis acidpromoted allylation of various electrophiles with allyltrimethysilane. Gloeosporone, epothilone a, the cdsubunit of spongistatins, and the c10c20 subunit of rhizoxin a, the keck allylation has also been utilized to form substituted tetrahydropyrans enantioselectively, moieties found in products such as phorboxazole and bryostatin 1. In particular, the hosomisakurai reaction, which involves the lewis acid promoted addition of allylsilanes to acetals and related electrophiles, has found. Highly stereoselective allyl additions are possible. Directed catalytic hosomisakurai reaction, chemistry a european journal on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. The asymmetric models will be mainly focused thereinto. Only catalytic amounts of lewis acid are needed in some newer. A stereoselective reductive hosomisakurai reaction.
Nov 23, 2012 counteranion control enables the enantioselective, organo lewis acid catalyzed hosomisakurai reaction of heteroaromatic aldehydes and allylsilanes using an easily handled disulfonimide precatalyst see scheme. High diastereoselectivity in hosornisakurai reaction on metalcomplexed. The sequence employs the newly developed reagent, 41,3dithian2yl2butenyltrimethylsilane 6, which serves as an annulating agent by a combination of michael addition and intramolecular hosomi sakurai reaction. Experimental data and spectral characterization for new products pdf. The catalyst is a chiral complex that contains titanium as a lewis acid. Files available from the acs website may be downloaded for. Idpi catalysis the hosomisakurai allylation and a mukaiyama aldol reaction with. The singapore story memoirs of lee kuan yew free download. High diastereoselectivity in hosornisakurai reaction on. Total synthesis of dehaloperophoramidine using a highly. Asymmetric cyanosilyation is a powerful method to convert carbonyls to chiral, configurationally stable cyanohydrins. New chiral allylaminosilanes and their use in asymmetric. This reaction was applied to the straightforward enantioselective syntheses of nboc dalloisoleucine 7 and disoleucine 8 from a.
The addition of allylsilanes to carbonyl compounds under lewis acid conditions, first described by sakurai and hosomi,1 has been widely applied to the synthesis of homoallylic alcohols which are important building blocks in organic synthesis, and the possibility of using this reaction for asymmetric synthesis has attracted considerable attention. A stereoselective reductive hosomisakurai reaction organic. We recently reported i an unusual, endoselective, conjugate allylation on 2arylidene1tetralone tricar bonylchromium complex2 by hosomisakurai reac tion3. Several allyltrimethoxysilanes have been synthesized and used for the asymmetric reaction. Recent developments in the catalyzed hosomisakurai reactions. The sakurai reaction also known as the hosomisakurai reaction is the chemical reaction of carbon electrophiles such as a ketone shown here with allylic silanes catalyzed by strong lewis acids.
1574 390 1523 947 1275 1206 1056 121 1386 314 596 75 1303 1562 930 971 586 648 82 926 773 1353 1070 175 569 690 1184 771 108 523 224 1153 374 860 1102 97 794 316 1236 141