T. Hagen

[2 + 4] Cycloaddition reactions of dialkylaminobis(trifluoromethyl)boranes with 1,3-dienes, β-unsaturated carbonyl compounds and methyl methacrylate. Crystal structures of (CF3)2BNR2CH2C(Me)C(Me)CH2, R = Me and Et, and (CF3)2BNEt2CH2CHC(Me)O

Hitherto unknown [2 + 4] addition reactions of aminoboranes were observed when dialkylaminobis(trifluoromethyl)boranes (CF3)2BNR2, R = Me and Et, were treated with a variety of 1,3-unsaturated compounds of the type XCR3CR2CHR1, where X = CH2 or O. The cycloaddition products of the general formula (CF3)2BNR2CHR1CR2CR3X were obtained in high yields. Ring closure was sterically hindered when the enone was OC(Me)CHCMe2, the B-alkylation product (CF3)2B(NHMe2)CH2C(O)CHCMe2 being formed instead by an ene reaction. Twelve novel boracyclohexene derivatives were isolated and characterized by multinuclear NMR spectroscopy and by mass spectrometry, and IR and Raman spectroscopy. The crystal structures of the compounds (CF3)2BNR2CH2-CMeCMeCH2, R = Me and Et, and (CF3)2BNEt2CH2CHCMeO have been determined by X-ray diffraction studies. They show that the BN and BCF3 bonds are somewhat longer than those in acyclic amine adducts of bis(trifluoromethyl)boranes. Furthermore, evidence is presented for steric congestion of the ring substituents.

[2 + 2 Cycloaddition reactions of dialkylaminobis(trifluoromethyl)boranes with isocyanates and isothiocyanates. Crystal structures of (CF32BNMe2CONtBu, (CF32BNMe2CSNtBu, (CF32BNPhC(NMe2)S and (CF3)2BNMeC(NEt2)OCONMe

Abstract The reactions of (CF3)2BNME2 (D1) and (CF3)2BNEt2 (D2) with isocyanates and isothiocyanates have been studied. At or near room temperature the CN bonds of RNCO and RNCS enter into [2+2] cycloadditions with the BN bond of D1 to yield the four-membered rings (CF3)2 BNMe 2 CON R; R = Me (I), tBu (II), Ph (III), CF3 (IV), and (CF3)2 BNMe 2 CSN R; R = Me (V), Et (VI), tBu (VII), Ph (VIII) and p-FC6H4 (IX) respectively. I, V, VI, VIII and IX rearrange at ≈60°C to form the isomers (CF3)2 BNMeC(NMe 2 )O (XI) and (CF3)2 BNRC(NMe 2 )S ; R = Me (XII), Et (XIII), Ph (XIV) and p-FC6H4 (XV), respectively. At room temperature D2 reacts with MeNCO to yield (CF3)2 BNMeC(NEt 2 )O (X) directly. X and XI reversibly incorporate MeNCO to form the six-membered heterocycles (CF3)2 BNMeC(NR 2 )OCON Me; R = Me (XVI) and Et (XVII). The structures of II, VII, XIV and XVII have been established by single crystal X-ray diffraction studies. The bond distances indicate that the π-bonding is delocalized over OCN (sp2), SCN (sp2 and SCN2 (sp2) fragments in II, VII and XIV, respectively. Furthermore, the π-character of the exocyclic CN bonds in XIV and VII, while considerable, is lower than that of the exocyclic CO(S) bonds in II, VII and XVII. The other structural assignments were based on mass spectrometry and vibrational and multinuclear NMR spectra.

BC bond formation by ene-type reactions of dimethylaminobis(trifluoromethyl)borane with nitriles and carbonyl compounds. Crystal structure of (NCCH2)(CF3)2B · NHMe2

Abstract Dimethylaminobis(trifluoromethyl)borane, (CF3)2BNMe2 (A), reacts with nitriles RCH2CN | to yield triorganoboron adducts | NCCHR)(CF3)2B · NHMe2 (R  H (I), Cl (II), Me (III) and Et (IV)). Analogously carbonyl compounds of the general formula R2C(O)CH2R1 form the respective complexes (R2C(O)CHR 1)(CF3)2B · NHMe2: R1  H, R2  tBu (V), R1  H, R2  Ph (VI), R1  H, R2  CCHCHC(Me)O (VII), R1  H, R2  Me (VIII), R1  H, R2  CHCMe2 (IX), R1  H, R2  OMe (X), R1  H, R2  OtBu (XI), R1  H, R2  OSiMe3 (XII), R1  H, R2  OC(Me)CH2 (XIII), R1  H, R2  OCH2CHCH2 (XIV), R1  H, R2  OtBu (XI), R1  OSiMe3 (XII), R1  H, R2  OC(Me)CH2 (XIII), R1  H, R2  OCH2CH CH2 (XIV), R1  H, R2  NMe2 (XV), R1  H, R2  NEt2 (XVII), R1  Cl,R2  OEt (XVIII), R1  Me, R2  OMe (XIX), R1  Et, R2  OMe (XX), R1  C(O)OMe, R2  OMe (XXI), R1  C(O)OtBu, R2  OtBu (XXII), R1, R2  CH2OCH2 (XXIII). Their identities have been confirmed by multinuclear NMR, IR, and mass spectroscopy. The crystal and molecular structure of I has been determined by an X-ray diffraction study. Individual molecules are linked to form infinite chains through hydrogen bonding. The BC (1.627(3) A (BCF3) and 1.629(4) A (BCH2CN)) and BN bond lengths (1.600(3) A are normal.

BN cleavage of the azoniaboratacyclopropane ring by H2O and by carbonyl and nitrile derivatives: crystal structure of (CF3)2B(OH)CH(SiMe3)NHMe2, (CF3)2 BCH(SiMe3NMe 2CMe2O and (MeC(O)NH)(CF3)2BCH(SiMe3)NHMe2

Abstract 1,1-Dimethyl-2,2-bis(trifluoromethyl)azoniaboratacyclopropane derivatives (CF3)2 BCHRN Me 2 (R = H (I), SiMe3 (II)) react with H2O with cleavage of the NB bond to form (CF3) 2B(OH)CHRNHMe2 (R = H (III), SiMe3 (IV)). Carbonyl compounds R1R2CO are inserted into the NB bond of I and II to yield the five-membered heterocycles (CF3)2 BCHRNMe 2 CR 1 R 2 O (R = H, R1 = R2 = Et (V); R = SiMe3, R1 = H, R2 = Me (VI), R1 = R2 = Me (VII), Et (VIII), R1 = Me, R2 = CH CMe2 (IX), CCMe(CH 2 ) 2 C H2) (X). Similarly nitriles insert to form (CF3)2 BCHRNMe 2 CR 1 N (R = H, R1 = CHClME (XI); R = SiMe3, R1 = Me (XII), CHClME (XIII), Ph (XIV)). The reaction of H2CCHCH2CN with II is accompanied by a shift in the CC bond whereby the substituent R1 = trans-CHCHMe (XV) is formed. Hydrogen cyanide combines with II to yield (CF3)2B(CN)CH(SiMe3)NHMe2 (XVI). The nitrile derivatives XI–XIV are hydrolysed with formation of (R1C(O)NHCF3)2BCHRNHMe2 (R = H, R1 = CHClME (XVII; R = SiMe3, R1 = Me (XVIII), CHClME (XIX), Ph (XX)). The novel boranes have been characterized by elemental analyses, multinuclear NMR, IR and mass spectra. The structures of IV and VII in a mixed crystal and of XVIII have been investigated crystallographically. In the solid state, IV and XVIII show intramolecular NH ⋯ O hydrogen bondings which leads to formation of five- and seven-membered rings respectively. Steric repulsion between the CF3 and SiMe3 groups leads to large BCSi bond angles (average, 124.1(8)°) and variable BCHSiN bond distances (1.604) A in VII to 1.690(4) A in IV).

Novel heterocycles from alkylamino-bis(trifluoromethyl) borane, (CF3)2BNR2, and isocyanides. Crystal and molecular structure of (NC)(CF3)2B · NHMe2,

Abstract Dialkylamino-bis(trifluoromethyl)boranes, (CF 3 ) 2 BNR 2 1 [R 1 = Me ( A ), Et ( B )] react at −20°C with t BuNC to form the respective adducts ( t BuNC)(CF 3 ) 2 BNR 2 1 [R 1 = Me ( I ), Et ( II )]. At 20°C these eliminate isobutylene to yield the amine boranes (NC)(CF 3 ) 2 B · NHR 2 1 [R 1 = Me ( III ), Et ( IV )]. i PrNC combines with A in a 2: 1 ratio to yield the four-membered heterocycle and in a 2:2 ratio to form . Heterocycles corresponding to VI with R = n Bu ( VII ), Et ( VIII ) and Me ( IX ) were obtained by the respective reactions of n BuNC, EtNC and McNC with A. The reaction of PhCH 2 NC with A leads to the formation of the heterobicyclo-octane ( X ). The novel boron compounds have been characterized by multinuclear NMR, IR and mass spectra. The structures of III, VIII and X have been investigated by single-crystal X-ray diffraction.

Alkylation of dimethylaminobis(trifluoromethyl)borane by 1-alkenes

Dimethylaminobis(trifluoromethyl)borane, (CF3)2BNMe2 (A), undergoes B-alkylation on treatment with 1-alkenes of the general formula (R1CH2)(R2)CCH2 to yield triorganoboron adducts Me2(H)NB(CF3)2CH2(R2)CCHR1(R1 H, R2Me (I); R1H, R2  CH2(CF3)2BNHMe2 (II); R1Me, R2 Et (III); R1H, R2CH2(tBu) (IV); R1H, R2Ph (V); R1H, R2 CHCMe2 (VI); R1Ph, R2H (VII); R1nPr, R2H (VIII); R1 iPr, R2H (IX)). In contrast, monosubstituted ethene derivatives (R2)CHCH2(RsBu, Ph, Mes, Me3Si, Et3Si) react with A to form the corresponding methylmethyleneimine boron adducts H2CN(Me)B(CF3)2CH2C H2R2 (X, XII–XV). With (tBu)(Me)CCH2, A undergoes both types of reaction, yielding a 1/4 mixture of Me2(H)NB(CF3)2CH2 (tBu)CCH2 (XIa) and H2CN(Me)B(CF3)2CH2CH(Me)(tBu) (XIb). Whereas I–IX and XIa are formed by an ene-type reaction, X and XIb–XV result from a shift of a hydride from the dimethylamino group to the alkylating substituent. The novel boranes have been characterized by elemental analysis and multinuclear NMR, IR and mass spectroscopy.

Addition von Dimethylamino-bis(trifluormethyl)boran an endständige Mehrfachbindungen: die N(CH3)2-Gruppe als Hydridlieferant

Abstract (CF 3 ) 2 BNMe 2 ( I ) was allowed to react with 3,3-dimethyl-1-butyne, 3,3-dimethyl-1-butene, hexafluoroacetone and trifluoroacetonitrile to yield the methylmethyleneimine-boranes (CH 3 ) 3 CCHCHB(CF 3 ) 2 ·(CH 3 )NCH 2 ( II ), (CH 3 ) 3 CCH 2 CH 2 B(CF 3 ) 2 ·(CH 3 )NCH 2 ( III ), (CF 3 ) 2 C(H)OB(CF 3 ) 2 ·(CH 3 )NCH 2 ( IV ) and CF 3 C(H)NB(CF 3 ) 2 ·(CH 3 )NCH 2 ( V ), respectively. The formation of II-V proceeds via a novel hydride shift with the N(CH 3 ) 2 group of I acting as hydride source. The novel boranes II-V have been characterized by multinuclear NMR, IR and mass spectra.

Oxa-azonia-boratacyclopentanes by insertion of dimethylaminobis(trifluoromethyl)borane into epoxides

Dimethylaminobis(trifluoromethyl)borane, (CF3)2BNMe2 (A), reacts with epoxides of the general formula to yield five-membered heterocycles (CF3)2, R = Me (1), CH,F (2), CF3 (3), Et (4), Bz (5). With R = Ph a 1:2 mixture of the isomers (CF3)2O (6a) and (CF3)2 (6b) is obtained. To the contrary, and A form the borane-dimethylamine adduct (H2C=CMe—CH2-O)(CF3)2B • NHMe2 (7). The compounds have been characterized by elemental analyses, multinuclear NMR, IR and mass spectra.

Cycloaddition reactions of dialkylaminobis(trifluoromethyl)boranes with isocyanates and isothiocyanates

Abstract The reactions of (CF 3 ) 2 BNMe 2 ( A1 ) and (CF 3 ) 2 BNEt 2 ( A2 ) with isocyanates and isothiocyanates have been studied. Near room temperature the C N bonds of RNCO and RNCS undergo [2+2] cycloaddition with the BN bond of A1 to yield the four-membered rings B . I, V, VI, VIII and IX rearrange at −60°C to form the isomers C . At room temperature A2 reacts with MeNCO to yield directly X. Both X and XI incorporate reversibly MeNCO to form the six-membered heterocycles D . The structures of II, VII, XIV and XVII were established by single-crystal X-ray diffraction methods. The other structural assignments are based on mass spectrometry and vibrational and multinuclear NMR spectra.

The reaction of (CF3)2B=NMe2 with nitriles and carbonyl compounds: novel hydride transfer competing with ene reaction

Abstract Bis(trifluoromethyl)-dimethylaminoborane, (CF 3 ) 2 BNMe 2 (1), which is obtained by nucleophilic trifluoromethylation of Cl 2 BNMe 2 with CF 3 Br/ P(NEt 2 ) 3 in polar solvents, reacts readily with nitriles and carbonyl compounds. Typical reactions are outlined in eq.(1). These can proceed either as ene reaction with rearrangement and (C)H→(N)H proton transfer (a,b) or, if no transferable proton is available, alternatively by (NCH 2 )H→(C)H hydride shift (c,d). The competition between the proton and the unprecedented hydride transfer pathways has been investigated for a considerable number of carbonyl and nitrile reactants.