Borinic acid esters

Chiral ketones.3 Asymmetric hydroboration of a prochiral alkene with monoisocampheylborane followed by a second hydroboration of a nonprochiral alkene provides a chiral mixed trialkylborane. This product reacts with acetaldehyde with elimination of a-pinene to give a chiral borinic acid ester in 73-100% ee. Treatment of this intermediate with a,a-dichloromethyl methyl ether (2,120 5, 200-203) and lithium triethylcarboxide followed by oxidation results in an optically active ketone in 60-90% ee. [Pg.518]

Asymmetric hydroboration 2171 of prochiral alkenes with monoisopinocampheyl-borane in the molar ratio of 1 1, followed by a second hydroboration of non-prochiral alkenes with the intermediate dialkylboranes, provides the chiral mixed trialkylbo-ranes. Treatment of these trialkylboranes with acetaldehyde results in the selective, facile elimination of the 3-pinanyl group, providing the corresponding chiral borinic acid esters with high enantiomeric purities. The reaction of these intermediates with base and dichloromethyl methyl ether provides the chiral ketones (Eq. 130)2l8>. A simple synthesis of secondary homoallylic alcohols with excellent enantiomeric purities via B-allyldiisopinocampheylborane has been also reported 219),... [Pg.80]

Nitrogen-donor macrocycles have also been prepared with other heteroatoms in the ring but not coordinated to the metal. Schrauzer (124) observed that chelate complexes (LVI) could be obtained when certain metal salts were present in the reaction of borinic acid ester... [Pg.19]

Cyclic horonic from borinic acid esters... [Pg.41]

Trimethylamine oxide Borinic acid esters from boranes... [Pg.46]

Borinic acid esters from hydroxy compds. OH -> O-BR ... [Pg.46]

Borines s. Boranes, Phosphite borines. Phosphorous triamide borines Borinic acid esters... [Pg.222]

A mixture of triisobutylborane, o-tolyl borate, and borane in tetrahydrofuran stirred 2 hrs. at 100° under Ng, cooled, pentane added followed by 1-pentene and LiAlH4 in ether at 0°, stirred 0.5 hr. at this temp., then ice-cold NaOH-soln. added diisobutyl-n-pentylborane. Y 85%. Also isolation of the intermediate o-tolyl diisobutylborinate (Y 84%), and f. borinic acid esters as well as borinic acids s. H. C. Brown and S. K. Gupta, Am. Soc. 95, 2802 (1971). [Pg.161]

Borazoles via B-halogenoborazoles s. 13, 652 Borinic acid esters from trialkoxyboroxines... [Pg.210]

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