Allylmagnesium, addition

The 5-oxohexanal 27 is prepared by the following three-step procedure (1) 1,2-addition of allylmagnesium bromide to an a, / -unsaturated aldehyde to give the 3-hydroxy-1,5-diene 25, (2) oxy-Cope rearrangement of 25 to give 26, and (3) palladium catalyzed oxidation to afford 27. The method was applied to the synthesis of A -2-octalone (28), which is difficult to prepare by the Robinson annulation[25]. 

Quinoxalines undergo facile addition reactions with nucleophilic reagents. The reaction of quinoxaline with allylmagnesium bromide gives, after hydrolysis of the initial adduct, 86% of 2,3-diallyl-l,2,3,4-tetrahydroquinoxaline. Quinoxaline is more reactive to this nucleophile than related aza-heterocyclic compounds, and the observed order of reactivity is pyridine < quinoline isoquinoline < phenan-thridine acridine < quinoxaline. ... 

Glyoxal-sodium bisulfite, 30, 86 Glyoxylic acid, w-butyl ester, 35, 18 ethyl ester, diethyl acetal, 35, 59 Grignard reaction, addition to ethyl sec-butylidenecyanoacetate, 35, 7 allylmagnesium bromide with of,(3-di-bromoethyl ethyl ether, 36, 61 allylmagnesium chloride with a,/3-di-bromoethyl ethyl ether, 36, 63 ethylmagnesium bromide with tin tetrachloride, 36, 86... 

The oxepane and oxepanone derivatives 51 and 52 respectively, were made by allylindation of, or allylmagnesium bromide addition to, acyclic tetrakis(tetrahydrofuranyl) dialdehydes. The solid state conformation of 52 was determined by X-ray diffraction analysis <00JOC4303>. 

Sphydrofuran is a structurally unique secondary metabolite produced by a variety of Streptomycetes strains. The first total synthesis of this compound was based in the use of RAMA to catalyze the aldol addition of chloroacetaldehyde with DHAP that provides two of the three chiral centers of the target molecule. The third quaternary center was introduced via a highly diastereoselective Grignard addition of allylmagnesium bromide (Scheme 4.17) [41]. 

From Hard Allylic Organometallics. The most common preparation of allylic boranes and boronates is the addition of a reactive allylic metal species to a borinic or boric ester, respectively (Eqs. 10 and 11). Preparations from allyllithium, " " allylmagnesium, and allylpotassium " ° reagents are all well known. These methods are popular because the required allylic anions are quite easy to prepare, and because they generally lead to high yields of products. 

Another method for the alkylidenation of aldonolactones uses addition of organ-ometallic reagents [78]. For example, Lin et al. [85] described an efficient route to conjugated anomeric dienes or aldehydes based on the reaction of aldono-1,4- and aldono-1,5-lactones (1, 62) with allylmagnesium chloride (Scheme 19), giving allyl hemiacetals (e.g., 63a, b). Hemiacetal can be dehydrated [e.g., with (CF3C0)20] to produce dienes 64a, b, or ozonolyzed (e.g., to give 65). 

Scheme 19 C-Glycosyl derivatives by addition of allylmagnesium chloride to aldonolactones...

Jurczak and Kiegiel reported that additions of allylmagnesium chloride and allyl bromide in the presence of Zn to iV-methyl and W-phenylglyoxyloyl-(2R)-borane-10,2-sultam occurred in a diastereoselective manner. Similarly, the Lewis acid mediated addition of allyltrimethylsilane also gave good diastereoselectivity and in the case with TiCU a change of direction of asymmetric induction was observed <99TL1009>. 

The addition of allylmagnesium halides (2 equiv.) to 1,3-azadienes affords after in situ alkylation dihomoallylamines, which are useful intermediates in the synthesis of azepines or related heterocycles. Activation of the C=N moiety of aldimines by 1-benzotriazolyltrimethylsilane minimizes side reactions. The mechanism involves reversible addition of BtTMS (216) to the imine 217 followed by displacement of the benzotriazolyl group by a Grignard reagent (equation 148). ... 

Other conjugated terminal enynes reacted in a similar fashion but the more substituted the double bond, the less efficient the allylzincation reaction168,172,173. By comparison, organolithium reagents and allylmagnesium bromide underwent conjugate addition to terminal enynes with nucleophilic attack of the double bond168,171,172. 

Tetsuaki Tanaka of Osaka University has reported (Tetrahedron Lett. 45 75, 2004) what appears to be a general route to alkylated quaternary centers, based on the Ti-mediated addition of allylmagnesium chloride to the Sharpless-derived epoxy ether 4. Remarkably, the conversion of 6 to 7 works equally well. 

We have put forward (J. Am. Client. Soc. 2004, /26, 13900) an alternative approach to the enantioselective construction of cyclic quaternary centers. Addition of phenylacetylene to cyclopentanone followed by dehydration and Shi epoxidation gave the epoxide 10. Opening of the epoxide with allylmagnesium chloride proceeded with inversion, to give II. The alcohol 11 can also be carried on to bicyclic products, exemplified by the sulfone 12. 

---