Allyl Grignard reagent

Alkylidene malonate substitute complex (89) undergoes diastereoselective Michael-type additions with a number of nucleophiles including organolithiums, Grignards (5ee Grignard Reagent, allyl tributylstannane, and ketene silyl... 

Silacyclobutane monomers with aryl and alkylaryl substituents were prepared in multi-gram quantities from reaction of commercially available 1,1 -dichloro-1 -silacyclobutane and 1 -chloro-1 -methyl-1 -silacyclobutane precursors with suitable Grignard reagents. Allyl-substituted AB and AB2 type monomers were prepared from treatment of intermediate diorganochlorosilanes and organodichlorosilanes, respectively, with allylmagnesium bromide. Selected structures of the monomers used in this work are represented in Figure 2. 

Structural rearrangements are not encountered with saturated Grignard reagents. Allylic and homoallylic systems can give products resulting from isomeriz-... 

A general method for the synthesis of l -alkenes is provided by the action of a Grignard reagent upon allyl bromide, for example ... 

If reaction does not occur when a little allyl bromide is first introduced, further addition must be discontinued until the reaction has commenced. Remove 2-3 ml. of the Grignard solution with a dropper pipette, add about 0-5 ml. of allyl bromide and warm gently to start the reaction after this has reacted well, add the solution to the main portion of the Grignard reagent. 

Conjugate addition of vinyllithium or a vinyl Grignard reagent to enones and subsequent oxidation afford the 1.4-diketone 16[25]. 4-Oxopentanals are synthesized from allylic alcohols by [3,3]sigmatropic rearrangement of their vinyl ethers and subsequent oxidation of the terminal double bond. Dihydrojasmone (18) was synthesized from allyl 2-octenyl ether (17) based on Claisen rearrangement and oxidation[25] (page 26). 

Allyl Complexes. Allyl complexes of uranium are known and are usually stabilized by cyclopentadienyl ligands. AEyl complexes can be accessed via the interaction of a uranium halide and an allyl grignard reagent. This synthetic method was utilized to obtain a rare example of a "naked" homoleptic allyl complex, U(T -C2H )4 [12701 -96-17, which decomposes at 0°C. Other examples, which are more stable than the homoleptic allyl complex have been synthesized, ie, U(allyl)2(OR)2 (R = alkyl), U(allyl)2X (X = halide), and U(allyl)(bipy)2. 

Pyrroles do not react with alkyl halides in a simple fashion polyalkylated products are obtained from reaction with methyl iodide at elevated temperatures and also from the more reactive allyl and benzyl halides under milder conditions in the presence of weak bases. Alkylation of pyrrole Grignard reagents gives mainly 2-alkylated pyrroles whereas N-alkylated pyrroles are obtained by alkylation of pyrrole alkali-metal salts in ionizing solvents. 

This procedure illustrates a general method for the preparation of 2-hydroxybicyclo[3.2.0]heptanes by copper(I)-catalyzed photobicyclization of 3-hydroxy-1,6-heptadienes, and a general route to the requisite dienes from allyl alcohols by conversion to 4-pentenals and treatment of the latter with vinyl Grignard reagents. 

Preparation of the aldehyde required for the synthesis of cyclothiazide (182) starts by carbonation of the Grignard reagent obtained from the Diels-Alder adduct (186) from allyl bromide and cyclopentadiene.The resulting acid (187) is then converted to the aldehyde (189) by reduction of the corresponding diethyl amide (188) with a metal hydride. 

Johnson s classic synthesis of progesterone (1) commences with the reaction of 2-methacrolein (22) with the Grignard reagent derived from l-bromo-3-pentyne to give ally lie alcohol 20 (see Scheme 3a). It is inconsequential that 20 is produced in racemic form because treatment of 20 with triethyl orthoacetate and a catalytic amount of propionic acid at 138 °C furnishes 18 in an overall yield of 55 % through a process that sacrifices the stereogenic center created in the carbonyl addition reaction. In the presence of propionic acid, allylic alcohol 20 and triethyl orthoacetate combine to give... 

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