Mercuration-boronation

Martin utilized indoleboronic acids in Pd-catalyzed coupling to great effect, and has improved upon the halogen-metal exchange route to indole-3-boronic acids by adopting a mercuration-boronation protocol as illustrated below for the preparation of 96 and 97 [115,116],... 

The iodination reaction can also be conducted with iodine monochloride in the presence of sodium acetate (240) or iodine in the presence of water or methanolic sodium acetate (241). Under these mild conditions functionalized alkenes can be transformed into the corresponding iodides. AppHcation of B-alkyl-9-BBN derivatives in the chlorination and dark bromination reactions allows better utilization of alkyl groups (235,242). An indirect stereoselective procedure for the conversion of alkynes into (H)-1-ha1o-1-alkenes is based on the mercuration reaction of boronic acids followed by in situ bromination or iodination of the intermediate mercuric salts (243). 

Mercuration. Mercury(II) salts react with alkyl-, alkenyl-, and arylboranes to yield organomercurials, which are usehil synthetic intermediates (263). For example, dialkyhnercury and alkyhnercury acetates can be prepared from primary trialkylboranes by treatment with mercury(II) chloride in the presence of sodium hydroxide or with mercury(II) acetate in tetrahydrofuran (3,264). Mercuration of 3 -alkylboranes is sluggish and requires prolonged heating. Alkenyl groups are transferred from boron to mercury with retention of configuration (243,265). 

Boron trifluoride-acetic acid complex Harshaw Chemical Co., Allied Chemical Co. 1,5-Cyclooctadiene A, MCB Sulfur dichloride MCB Boron trifluoride etherate EK, MCB Mercuric acetate MCB Norbornene MCB Calcium carbide MCB Pinacol EK, MCB... 

Compound (1) phosphorylates phosphate monoesters and alcohols, although with the latter a considerable excess of alcohol is necessary to obtain satisfactory yields. In the absence of mercuric ions the milder phosphorylating species (3) can be isolated which converts monoalkyl phosphates to pyrophosphate diesters in good yield but does not react appreciably with alcohols unless catalytic amounts of boron trifluoride are added. Amine salts of (3) are converted to phosphoramidates on heating. In the presence of silver ions, O-esters of thiophosphoric acid behave as phosphorylating agents and a very mild and convenient procedure suitable for preparing labile unsymmetrical pyrophosphate diesters, such as the... 

Arsenic disulfide, boron trisulfide and mercuric sulfide all ignite in chlorine at... 

Boron trifluoride etherate, co-catalyst, 53, 30, 32 a-Bromination, selective of aralkyl ketone, 53, 111 Bromine, with 3-chlorocyclo-butanecarboxylic acid and mercuric oxide to give 1-bromo-3-chlorocyclobutane, 51, 106... 

Under the catalysis of mercuric oxide and boron trifluoride-diethyl ether, the reaction of methanol with 1,2-hexadiene afforded 2,2-dimethoxyhexane [6]. Hydration with sulfuric acid led to methyl n-butyl ketone [6],... 

An efficient process for one-carbon homologation to aldehydes is based on cyclic boronate esters.17 These can be prepared by hydroboration of an alkene with dibromobor-ane, followed by conversion of the dibromoborane to the cyclic ester. The homologation step is carried out by addition of methoxy(phenylthio)methyllithium to the boronate ester. The migration step is induced by mercuric ion. Use of enantioenriched boranes and boronates leads to products containing the groups of retained configuration.18... 

Moureu investigated the addition of alcohols, catalyzed by sodium methoxide, to acetylenic esters and has shown that enol ethers are formed as primary adducts. It has been shown that compounds such as potassium cyanide, a mixture of mercuric oxide, boron trifluoride,... 

Amino guanidine bicarbonate, Amm acetate, Amm phosphate, Amm sulfate, apatite, asbestos, Ba sulfate, boron nitride, cerium oxide, cryolite, dicyandiamide, dimethyl oxamide, dimethyl urea, d sodium phosphate, mercurous nitrate, methylene urea,... 

Vinylation can also be done by Pd-catalysed cross-coupling in which one component is used as a halide or triflate and the other as a stannane (Stille reaction) or boronic acid (Suzuki reaction). Entry 9, Table 11.3, is an example of the use of a vinylstannane with a haloindole. lndole-3-boronic acids, which can be prepared by mercuration/boration, undergo coupling with vinyl triflates (Entry 10). 

Treatment with mercuric chloride or methyl fluorosulfonate before the oxidation step initiated the migration of a second alkyl group from boron to carbon, and a synthesis of tertiary alcohols was thus at hand [284]. 

KUCHEROV REACTION. The hydration of acetylenic hydrocarbons with dilute sulfuric acid in the presence of mercuric sulfate or boron trifluoride as catalyst. 

In further studies, Matteson et a/.10,11 reported relative rates of substitution of various boronic esters by mercuric chloride details are given in Table 3. The solvent used was a mixture of ethanol (88 %), water (8 %), and glycerol (4 %), buffered with sodium acetate and acetic acid, and reactions were run in the presence of added sodium chloride. Under these conditions, the kinetics of reaction of benzylboronic ester with mercuric chloride were found to obey the rate law... 

Matteson and Kramer11 suggested that a glycerol ester of the boronic acid is converted into a hydroxide complex, as in equation (6), and this complex is then attacked by mercuric chloride in the rate-determining step (7). 

RELATIVE RATE COEFFICIENTS FOR THE SUBSTITUTION OF ESTERS OF BORONIC ACIDS, RB(OH)2, BY MERCURIC CHLORIDE10 11... 

Second-order rate coefficients for the reaction of some boronic esters with mercuric chloride in methanol were reported by Matteson and Allies13 details are in Table 4. The solution was buffered with sodium acetate/acetic acid, and the observed rate equation was found to be... 

SECOND-ORDER RATE COEFFICIENTS (I.mole" .See 1) AND ACTIVATION PARAMETERS FOR THE SUBSTITUTION OF BORONIC ESTERS BY MERCURIC CHLORIDE IN SOLVENT... 

In one case, this reagent was superior to mercuric oxide/boron trifluoride (3, 136), ceric ammonium nitrate (4,74), or sulfuryl chloride (7, 350). 

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