Crotyl chloride , ether

Experimental. Butenylmagnesium chloride was prepared from crotyl chloride and magnesium chips in ether. Decomposition reactions of butenylmagnesium chloride were carried out at room temperature using H20 and D20. Butenes were condensed at — 20 °C. and analyzed on a FB-4 Shandon ionization chromatograph. 

These compounds have been obtained by the addition of cyclooctadiene to an equimolar mixture of /i3-allyl or /d -crotyl-(2,4-pentanedionato)palladiuni(II) and tetrafluoroboric acid in methylene chloride-ether solution.1 If silver tetrafluoroborate is on hand, the slight modification described below obviates the need to prepare the /3-diketonate complex as an intermediate. 

An additional element of complication in preparing the allyl ethers utilizing the salts of hydroxypyridines lies in the intervention of SN2 displacements. Thus the sodium salt of 2-pyridone on treatment with crotyl chloride or with 3-chloro-1 -butene afforded the same compound, viz., l-crotyl-2-pyridone5 [Eq. (1)]. 

Allylic chlorides, e.g., allyl, methallyl, and crotyl chlorides, are very reactive and are employed in the synthesis of unsaturaled ethers Besides the usual coupling of the sodium alcoholate and halide in alcohol solutions other conditions have been described, including reaction of the alcohol and unsaturated halide in the presence of potassium carbonate or sodium hydroxide in acetone or water. The combination of anhydrous potassium carbonate and acetone is widely used in the preparation of allyl aryl ethers the reaction is aided by the addition of finely powdered potassium iodide. ... 

The reaction of crotyl chloride with TMSCI under Barbier conditions yields the same ratio of products as the reaction of the preformed crotyl Grignard reagent with TMSCI in ether [Eq. (64) 130]. 

To a solution of 2.27 g heptaldehyde (19.9 mmol) in 20 mL saturated aqueous NH4CI and 4 mL THF, was added 1.56 g zinc (24 mmol) and 2.36 mL crotyl chloride (24 mmol). The reaction mixture exposed to the air was stirred overnight at room temperature, and the suspension (containing zinc salts) was then extracted with Et20, and the ether layer was dried over MgS04. Upon evaporation of Et20, the residue was quickly passed through a silica gel pad to afford 2.97 g 3-methyl-l-decen-4-ol as a 1 1 mixture of erythro to threo products, in a yield of 87.8%, Rf = 0.5 (EtOAc/hexane, 1 9). 

A solution of ( )-crotyl chloride (5.4 g, 60 mmol) and trichlorosilane (11.7 g, 86 mmol) in diethyl ether (10 mL) is added to a suspension of copper(I) chloride (0.20 g, 2.0 mmol) and triethylamine (7.2 g, 71 mmol) in diethyl ether (30 mL) at it. The reaction mixture is stirred for 1.5 h, and insoluble materials are filtered off. The filtrate is concentrated the residue is distilled to give ( )-crotyltrichlorosilane in 76% yield. SbFe (15.3 g, 86 mmol) is placed in a 50-mL flask and heated under vacuum for 2 h for drying. To this is added ( )-crotyltrichlorosilane (9.9 g, 52 mmol) drop by drop. An exothermic reaction takes place and... 

In the first step, reagent 7, developed by Hoffmann, is used lor asymmetric crotylation in order selectively to create the stereogcnic centers at C-10 and C-ll (dr >98 2).13 14 This produces compound 24, which is subsequently protected at C-11 as the p-mclh-oxyben/yl ether Protection is accomplished by reaction of the anion of the alcohol with commercially available p-methoxyben/yl chloride.15 16... 

Reaction (e) is also useful for preparing mixtures of ether adducts of allyl- ", crotyl- , propargyl- and benzylaluminum bromides. The organo bromides are used to insure enhanced reactivity (as compared with the chlorides) and less coupling (as compared with the iodides). 

According to Bharucha and Weedon263 fra/is-crotyl alcohol is formed when LiAlH4 (2 g) in anhydrous ether (150 ml) is dropped in 0.5-1 h into a stirred solution of 2-butyn-l-ol (3 g) in anhydrous ether (25 ml), and the mixture is then boiled under reflux for a further 3 h. After cooling, the excess of hydride is decomposed with ethyl acetate (14 ml), and saturated ammonium chloride solution (24 ml) is added. The mixture is then filtered and the ethereal layer is washed with water and dried (Na2S04 plus some K2C03). After removal of the ether the residue is distilled in a vacuum, yielding trans-crotyl alcohol (1.6 g) of b.p. 122° and n 1.4278. 

Addition of an T -allyl-Fp complex to this compound affords an T -aIlyl-Fp-substituted cycloheptatriene system. Two double bonds are involved in an (T -diene)iron complex. The remaining free double bond of the silyl enol ether attacks as a nucleophile at the cationic r -alkene-Fp moiety to form an (Tj -diene)iron complexed cyclopentane annulated cycloheptadienone. Treatment with CAN in methanol under carbon monoxide atmosphere releases the methoxycarbonyl-substituted free ligand (Scheme 4-25). Reaction of the Ti -dienyliumiron intermediate of Scheme 4-25 with an ( , Z)-isomeric mixture of ri -crotyl-Fp proceeds with high diastereoselectivity. Four new stereogenic centers are formed in the course of this formal [3+2] cycloaddition. A hetero [3+2] cycloaddition is also feasible between T -ailyl-Fp complexes and aromatic aldehydes in the presence of zinc chloride or titanium(IV) chloride to provide tetrahydrofuran derivatives (Scheme 4-26). A 1,2-shift of the iron complex fragment occurs in the course of this reaction. Employment of imines affords the corresponding pyrrolidines. ... 

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