Sakurai reaction, aza

Bismuth-Mediated Three-Component Aza-Sakurai Reaction. 85... 

Other magnetite-catalysed transformations have also been reported " Yus reported a one-pot multieomponent aza-Sakurai reaction, and in later work reported the direct amination of benzylic-alcohols. ... 

HomoallyUc amines are useful intermediates in the synthesis of biologically active compounds such as statin, conine, lobeline, sedamine, SKF-1(K)330-A, epothilone, p-lactams, p-amino acids, and many natural products. The synthesis of those interesting precursors is also possible starting from an imine instead of a carbonyl compound, through this kind of reactivity, known in this case as aza-Sakurai reaction [94, 95]. Its multicomponent version involves the in situ formation of that imine, and few recent examples are shown here. 

SCHEME 12.19 Four-component aza-Sakurai reaction catalyzed by FeSO -7HjO. 

SCHEME 12.20 Mechanistic proposal for the four-component aza-Sakurai reaction. 

Another elegant example of a multicomponent aza-Sakurai reaction was reported by Jarvo in 2009 [99]. In this case, Pd(OAc)j was used as catalyst both for the generation in situ of the aUylsilane from allyl trifluoroacetate and HMDS and also for the allylation of the in situ formed imine fi om the corresponding aldehydes and anisidine (H NPMP) (Scheme 12.22). This was concluded after a study base on competition experiments. This procedure allows the synthesis of a variety of homoallylic amines in good to excellent yields (67-96%), starting from different substrates including electron-rich aromatic and aliphatic aldehydes. 

SCHEME 12.22 Three-component one-pot, two-step transformation aza-Sakurai reaction catalyzed by PdfOAc). ... 

R. Martinez, D. J. Ramon, M. Yus, Adv. Synth. Catal. 2008, 350,1235-1240. Unmodified nano-powder magnetite catalyzes a four-component aza-Sakurai reaction. 

Keywords Aza-Sakurai allylationreaction Bismuth triflate C-C bond formation Mannich-type reaction Mukaiyama aldol reaction /V-AI koxycaihony I am ino sulfones Silyl nucleophiles... 

Another type of convertible nucleoside phosphoramidite, a derivative of (5 S)-5 -C-(5-bromo-2-penten-l-yl)-2 -deoxyribosylfuranosyl thymidine (49), has been reported. The synthesis of this phosphoramidite was stereoselective and involved a Sakurai reaction between 5 -C-thymidine aldehyde and allyltrimethylsilane. Seela has reported the synthesis of the ribosyl-phosphoramidite derivatives of 7-bromo- and 7-iodo-8-aza-7-deazapurine-2,6-diamine (50a,b) from advanced synthetic precursors and of the bromo- and iodo-derivatives at the 5-position of uracyl phosphoramidite (51a,b). He further described the effect on base-pair stability due to their incorporation into oligonucleotide duplexes. ... 

AZA-SAKURAI-HOSOMI REACTION ASSOCIATED WITH HYDROFORMYLATION... 

SCHEME 2 Azaheterocycle syntheses from the aza-Sakurai-Hosomi reaction. 

To continue this work, it seemed interesting to us to try to apply this methodology to develop a slightly more complicated skeleton, that of a quinolizidine. For this, the thesis work of Etienne Airiau included designing an effective strategy involving few steps and allowing the production of a substituted bicyclic structure. Hence, we applied the combination of the aza-Sakurai-Hosomi/CHC process followed either by a cross-metathesis reaction or by a new hydroformylation reaction. ... 

In this chapter, only the most recent multicomponent versions of the Hosomi-Sakurai reaction will be covered [68b], in particular those that allowed the synthesis of homoallylic ethers through the combination of an aldehyde (or ketone) with a silyl ether or the corresponding alcohol and an allylsilane (Scheme 12.13, Eq. 1). And also, the synthesis of homoallylic amines where the allylsilane reacts with an imine in situ formed from the carbonyl compound and an amine is known as aza-Sakurai reaetion (Scheme 12.13, Eq. 2). 

SCHEME 12.13 Multicomponent (aza-)Hosomi-Sakurai reactions synthesis of homoallylic ethers (Eq. 1) and synthesis of homoaUylic amines (Eq. 2). 

In this chapter, four different essential MCRs have been compiled, in particular Radziszewski, (aza-)Sakurai, Gewald, and Kabachnik-Fields reactions (Scheme 12.31). These reactions give access to five types of products substituted imidazoles, homoallylic ethers(amines), 2-aminothiophene derivatives, and a-aminophosphonates. The interest in these moieties is broadly recognized in the scientific community, since, among other properties, they are found in the structure of numerous biologically active natural or synthesized molecules. 

J. Org. Chem. 2(X)4, 69,4(X)5—4(X)6. Iodine as a very powerful catalyst for three-component synthesis of protected homoal-lylic amines, (c) J.-R. Ella-Menye, W. Dobbs, M. BUlet, P. Klotz, A. Mann, Tetrahedron Lett. 2005, 46, 1897-19(X). Unexpected 1,2 syn diastereoselectivity in the three-component aza Sakurai-Hosomi reaction, (d) M. Sugiura, K. Hirano, S. Kobayashi, J. Am. Chem. Soc. 2004, 126, 7182-7183. a-Aminoallylation of aldehydes with ammonia stereoselective synthesis of homoallylic primary amines, (e) M. BiUet, P Klotz, A. Mann, Tetrahedron Lett. 2(X)1,42, 631-634. Syn diastereoselectivity in the synthesis of homoallylamine using crotylsilane in the three-component reaction, (f) L. Niimi,... 

Treatment of the same nitrone with TMS-triflate at —40°C afforded a 79% yield of N-hydroxypiperidine 361 in an intramolecular aza-Prins reaction, which is certainly substantially assisted by the TMS group in the aUylic position (see Sakurai reaction) [129]. 

Another short synthesis of ( )-9a-ep(-quinolizidine 195C (rat-2318), by Mann and coworkers, is worth mentioning in view of its use of a Hnear hydroformylation of a homoallylamine (cyclohydrocarbonylation) to constmct the piperidine ring (Scheme 296). ° A three-component aza-Hosomi—Sakurai reaction between allyltrimethylsilane, butanal, and O-benzylurethane catalyzed by boron trifluoride was used to form the protected homoallylamine ( )-2319. The cyclohydrocarbonylation was then performed with a biphephos/rhodium(I) catalytic system in methanol, yielding the piperidine-containing hemiaminal 2320 in 84% yield. This... 

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