Dialkyl boron chlorides

Thakar and Subba Rao showed that reductions with diborane give the same result regardless of whether diborane is generated externally or produced internally by the action of NaBH4 and boron trifluoride or aluminum chloride. They found that alicyclic or dialkyl ketones are not reduced beyond the alcohol stage even under drastic conditions however, diaryl ketones are hydrogenolyzed under normal conditions, while aryl ketones or a,i5-unsatu-rated ketones are hydrogenolyzed, in part, under drastic conditions. 

In carrying out the alkylation of benzene the propylene tetramer is reacted with an excess of benzene in the presence of a Friedel-Crafts catalyst such as aluminum chloride, boron trifluoride, or hydrofluoric acid. With careful control of this reaction, yields of alkylate boiling from 500° to 650° F. are of the order of 80% of theory with the losses due to slight olefin degradation and dialkylation. Inspection of commercial aromatic products, believed to be typical of this process, indicates the composition to be that shown in... 

Carboxylic acid anhydrides or halides normally require the presence of a Lewis acid (often boron trifluoride) for Friedel-Crafts acylation of furans, though trifluoroacetic anhydride will react alone. Aluminium-chloride-catalysed acetylation of furan proceeds 7 x lO times faster at the a-position than at the P-position. 3-Alkyl-furans substitute mainly at C-2 2,5-dialkyl-furans can be acylated at a P-position, but generally with more difficulty. 3-Bromofuran is efficiently acetylated at C-2 using aluminium chloride catalysis. ... 

The P-N bond in phosphonous and phosphinous amides is cleaved easily and quantitatively by anhydrons hydrogen chloride at room temperature (6.143) and (6.144). Dialkyl phosphines, boron trichloride or hydrogen sulphide will effect similar cleavage. 

Naphthalene likewise yields two dialkyl derivatives the principal dialkylation product from the reaction of naphthalene and cyclohex-anol or cyclohexene with aluminum chloride as the catalyst has been shown to be 2,6-dicyclohexylnaphthalene, but from cyclohexanol and boron fluoride, 1,4-dicyclohexylnaphthalene is obtained. ... 

Orientation in di- or trialkylation may be regulated by controlling the vigor of the reaction. Relatively mild catalysts, such as boron fluoride (with an alcohol), hydrogen fluoride (with an olefin), or ferric chloride (with an alkyl halide), may lead almost excluavely to p-dialky-lation or 1,2,4-tiialkylation. Under more vigorous conditions, as with excess aluminum chloride at elevated temperatures, the m-dialkyl or sym-trialkyl derivative predominates. 

Methods for the synthesis of hop bitter acids are due to the elegant work of RiedI (78-84). The substrates are phloracylphenones, which are readily available from condensation of phoroglucinol with acid chlorides (Friedel-Crafts synthesis), nitriles (Hoesch synthesis) or carboxylic acids with boron trifluoride as catalyst. Carbon acylation of a phloracylphenone can give one monoalkylated derivative (13, Fig. 13), two dialkylated derivatives (14 and 15) and one tri- or tetra-alkylated derivative (16 and 17, respectively). The possibility of oxygen acylation can not be excluded. 

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