BF3-etherate

Parameter AICI3 AlBt3 BF3 BF3 etherate/H20 TiCl SnCl AICI3/HCI ddb"... 

In some instances, ring contraction is accompanied by cyclization to indole derivatives. For example, l-aryl-6-oxo-l,4,5,6-tetrahydropyridazines with a carboxyl or methyl group at position 3 give indoles when treated with an ethanolic solution saturated with hydrogen chloride or in the presence of BF3 etherate. 

Keto-5) , lOjff-epoxides (38) undergo diaxial opening with BF3-etherate in benzene to form the fluorohydrins (39). ... 

Schmidt reaction of indanones 803 by treatment with HN3-BF3 etherate gave 4,5-dihydro[5,l-a]tetrazoloquinoline 804 (92IJC(B)610)) (Scheme 142). 

The use of catalysts for a Diels-Alder reaction is often not necessary, since in many cases the product is obtained in high yield in a reasonable reaction time. In order to increase the regioselectivity and stereoselectivity (e.g. to obtain a particular endo- or exo-product), Lewis acids as catalysts (e.g. TiCU, AICI3, BF3-etherate) have been successfully employed." The usefulness of strong Lewis acids as catalysts may however be limited, because they may also catalyze polymerization reactions of the reactants. Chiral Lewis acid catalysts are used for catalytic enantioselective Diels-Alder reactions. ... 

V si sol in w and toluene approaches miscibility with acet. The polymer is prepd by dissolving mol equiv wts of the monomers in anhyd dioxane together with 1.5 mol equiv wt % of BF3 etherate as the catalyst. The mixt is then maintained at 40—50° for several weeks. The product is pptd in w and the solvent removed by steam distn... 

Lewis acids are also used in conjunction with acyl halides. The reagent Nal—BF3 etherate selectively cleaves ethers in the order benzylic ethers > alkyl methyl ethers > aryl methyl ethers. 

Acetylation of acetals or ketals can be accomplished with acetic anhydride and BF3-etherate. ° The mechanism with acetals or ketals also Involves attack at an alkenyl carbon, since enol ethers are intermediates. Ketones can be formylated in the a position by treatment with CO and a strong base. ... 

Many methods have been reported for the addition of allylic groups, including allyltrialkyltin compounds" (in the presence of BF3-etherate), as well as other allylic metal compounds." Allylic alcohols and homo allylic alcohols add to aldehydes in the presence of Sn(OT02 " For allylic halides, both activated... 

Reaction of alkenes with a disulfide and BF3 etherate Addition of H2S to carbonyl compounds or imines... 

Pyridone IV was converted to its sodium salt by treatment with an equimolar amount of sodium methoxide in methanol (see procedure below under formation of the 3-phenyl-2(lH)pyridone sulfonates). The sodium salt was next treated with the methyl ester of a-bromo-p-toluic acid, obtained by treatment of the acid with BF3 etherate. 

In other cyclisations to functionalised oxepanes, Rychnovsky and Dahanukar have shown that the epoxide 36 cyclises with BF3 etherate and TMSCN to form the oxepane 37 as single product <96TL339>, and Evans and Roseman have prepared a series of cyclic ethers by radical cyclisation of the acylselenides 38 (Scheme 8) <96JOC2252>. The major product was always the cw-isomer and the best yields were obtained with (TMSjaSiH. 

Modest diastereoselectivity was observed for the Michael addition reaction of rac-14 to 13 and these diasteromers 28-a/28-b could be separated and individually identified. The minor isomer 28-b was found to readily undergo conversion to benzoxathiin 30 when treated with BF3 etherate, presumably through the transient intermediate 29-b. The major isomer 28-a was converted by BF3 etherate to intermediate 29-a. Conversion to 30 required the use of the stronger Lewis acid TMSOTf, presumably due to the cis-stereochemistry between the methoxy and the neighboring hydrogen, making it more difficult to eliminate/aromatize. 

The effective half-time for this reaction at room temperature is 9 min in comparison with 79 min without BF3-etherate.[139]... 

More substituted and unactivated dienophiles such as 3-acetoxy-2-methyl-cyclopentenone, did not react with 112 even in the presence of BF3 etherate. 4-Acetylspiro[2.1.2.3]decen-9-one (128) could also be isolated under these con-... 

For preparation of allyl coumarins and dihydrofuranocoumarins by tandem Claisen rearrangement-cyclization the usual procedures required vigorous reaction conditions, workup procedures were tedious, and long reaction times led to low yields. The rearrangement of allyloxycoumarins 48 to dihydrofuranocoumarins 49 has been optimized in good yields in a sealed Teflon containers with BF3-ether in N-methyl-... 

Condensation of sulfoximine 717 with an aldehyde and benzotriazole produces Ar-[ -(bcnzotnazol-l -yl)alkyl]sul-foximine 718. Treatment with allyl silanes in the presence of BF3 etherate or with organozinc reagents allows substitution of the benzotriazolyl moiety in compound 718 to produce variety of substituted sulfoximines 719... 

M olivetol or analog, 1M citral in 10% BF3 etherate in benzene about eight hours at 5-10° C. Extract unreacted olivetol with dilute NaOH and evaporate in vacuum the ether to get about 20% yield of the trans THC, and 20% of the cis THC which can be converted to the active trans isomer by reacting with BBr3 in methylene chloride at -20° C for Vh hours. (TL 4947(1969)). Alternatively, the reaction can be carried out in 1 % BF3 etherate in methylene chloride to get 20% THC. 

Alternatively, 63 g (0.45M) BF3 etherate in 180 ml diglyme is added dropwise with stirring to 0.15 M of the indolyglyoxamide and 12 g NaBHi in 300 ml diglyme. Stir 12 hours at room temperature and evaporate in vacuum. Boil residue 2 hours with methanolic NaOH and evaporate in vacuum. Take up residue in ether, wash with water and dry, evaporate in vacuum to get the dialkyltryptamine in ca. 80% yield. 

Macrocyclization,3 A new route to cembranolides (3) involves intramolecular coupling of an alkoxyallyltin derivative (1) with an acetylenic aldehyde catalyzed by BF30(C2H5)2 (cf. 12, 513-514). Thus in the presence of BF3 etherate 1 cyclizes to 2 with syn-selectivity. The product is converted to the cembranolide 3 by hydrolysis of the enol ether and oxidation. 

Homoallyl ethers or sulfides.1 gem-Methoxy(phenylthio)alkanes (2), prepared by reaction of 1 with alkyl halides, react with allyltributyltin compounds in the presence of a Lewis acid to form either homoallyl methyl ethers or homoallyl phenyl sulfides. Use of BF3 etherate results in selective cleavage of the phenylthio group to provide homoallyl ethers, whereas TiCl effects cleavage of the methoxy group with formation of homoallyl sulfides. 

RCu BFy Yamamoto22 has reviewed the special properties of RCu combined with BF3 etherate or A1C13 (80 references). In particular, these reagents are generally superior to R2CuLi for conjugate addition to a,(3-enones such as 1. 

BF, or BF3 etherate can replace TiCl4 as the Lewis acid. But in order to effect clean reactions, the Lewis acid should be added to the aldehyde before addition of the lead reagent. The rate of reaction is highly dependent on the size of the R group. Transfer of an ethyl group is rapid, but a cyclohexyl group is transferred slowly even at 0°. Similar transfer does not obtain with R4Sn. 

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