Amines organoboranes

Dow Automotive has also been very active in this area Most of Dow s patents were authored by Sonnenschein and co-workers [88-94]. Patents describe a range of amine- and amidine-complexing agents and several de-complexing agents, quite similar to the 3M patents. These patents disclose amine organoborane complexes wherein the organoborane is a trialkyl borane and the amine is selected from the... 

Sodium borobydride reacts with Lewis acids in nonprotic solvents to yield diborane [19287-45-7] 2 6 which can then be used to generate other useful organoboranes such as amine boranes, alkyl boranes, and boron hydride clusters. 

Olefins are also the products of hydroboratlon of enamines, followed by treatment of the organoborane products with hot acid (543,544). The reduction of enamines with sodium borohydride and acetic acid (545) and the selective reduction of dienamines with sodium borohydride to give homo-allylic tertiary amines (138-140,225,546,547), has been applied to the synthesis of conessine (548) and other aminosteroid analogs (545,549-552). Further examples of the reduction of imonium salts by sodium borohydride can be found in the reduction of Bischler-Napieralski products, and other cyclic imonium salts (102). 

Organoboranes react with a mixture of aqueous NH3 and NaOCl to produce primary amines. It is likely that the actual reagent is chloramine NH2CI. Chloramine itself,hydroxylamine-O-sulfonic acid in diglyme, and trimethyl-silyl azide " also give the reaction. Since the boranes can be prepared by the hydroboration of alkenes (15-16), this is an indirect method for the addition of NH3 to a double bond with anti-Markovnikov orientation. Secondary amines can be prepared by the treatment of alkyl- or aryldichloroboranes or dialkylchlorobor-anes with alkyl or aryl azides. 

The regiospecific functionalization of the terminal alkyl group of simple amines or ethers with bis(pinacolato)-diborane leads to organoboranes. The latter have manifold applications in organic synthesis since the catalytic borylation process can be combined with a functional group transformation step, including Suzuki-Miyaura couplings, for the synthesis of elaborated molecules. Curiously, functionalization of the C-H atoms a to the heteroatom was not observed (Equation (22)). a... 

Organoboranes R2BH or R3B (R = C10H21, cyclohexyl or cyclooctyl etc.) react with hydroxylamine O-sulphonic acid or its mesityl derivative or with chloramine to form primary amines RNH2100 101. 

Hydroboration of alkenes generates organoboranes, which react with sodium azide in the presence of an aqueous acid to give primary amines (equation 58). Thus 1-nonene... 

An analogous reaction is the conversion of olefins into primary amines by the consecutive action of BH3. THF and trimethylsilyl azide171. The observation172 that organoboranes and chloramine give primary amines is the basis of an amine synthesis in which olefins are treated with the complex BH3 THF, followed by aqueous ammonia and aqueous sodium hypochlorite173. Imines are reduced by the chiral dioxaborolidine 162 to yield optically active amines. 1-Imino-l-phenylpropane, for instance, affords 1-phenylpropylamine in 73% enantiomeric excess (equation 59)174. 

The amination of organoboranes with H2NOZ-type reagents involves initial nucleophilic attack of NH2OZ on the organoborane to yield an organoborate complex followed... 

A number of protocols have been reported for the amination of organoboranes and have been reviewed in detail . 

A-Lithium and A-potassium derivatives of A-Boc 0-p-tosylhydroxylamines have been also reported to react rapidly with organoboranes to give A-Boc protected primary amines in modest to good yields (Scheme 28) . 

There are a number of reports on the nonsymmetric and symmetric amination of organoboranes and boronic esters with hydroxylamine O-sulfonic acid (HOSA) 3p . 

Sulfonylhydroxylamines and hydroxylamine O-sulfonic acid have found wide apph-cation in synthesis of amines from achiral or chiral organoboranes and boronate esters and the hydroboration-amination methodology is successfully used for direct amination of alkenes. 0-Sulfonyloximes were also found to be good reagents for synthesis of amines from organomagnesium, -copper and -zinc reagents. 

Conditions that permit oxidation of organoboranes to alcohols using molecular oxygen,139 sodium peroxycarbonate,140 or amine oxides141 as oxidants have also been developed. The reaction with molecular oxygen is particularly effective in perfluoroalkane solvents.142... 

The oxidation by amine oxides provides a basis for selection among non-equivalent groups on boron. In acyclic organoboranes, the order of reaction is tertiary > secondary > primary. In cyclic boranes, stereoelectronic factors dominate. With 9-BBN derivatives, for example, preferential migration of a C—B bond which is part of the bicylic ring structure occurs. 

Scheme 4.8. Alcohols, Ketones, Aldehydes, and Amines from Organoboranes...

Procedures for synthesis of chiral amines163 164 and halides165 166 167 based on chiral alkylbor-anes have been developed by applying the methods discussed earlier to the homochiral organoborane intermediates. For example, enantiomerically pure terpenes can be converted to trialkylboranes and then aminated with hydroxylaminesulfonic acid. 

Organoboranes react with a mixture of aqueous NH3 and NaOCl to produce primary amines.358 It is likely that the actual reagent is chloramine NH2C1. Chloramine itself,359... 

Synthesis of Primary Amines via the Reaction of Organoboranes with Trimethyl silyl Azide in Neutral Medium 2-exo-Norbornyl Amine. 

Distillation from lithium aluminum hydride serves to remove completely all traces of water and amine as is required for preparation of chiral organoboranes. 

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