4,5,6,7-Tetrachlorobenzo[d][1,3,2]dioxaborol- 2-ol as an effective catalyst for the amide condensation of sterically demanding carboxylic acids

[reaction: see text] 4,5,6,7-Tetrachlorobenzo[d][1,3,2]dioxaborole (4a) and 4,5,6,7-tetrachlorobenzo[d][1,3,2]dioxaborol-2-ol (4b) are effective catalysts for the dehydrative amide condensation between an equimolar mixture of carboxylic acids and amines. In particular, these catalysts are greatly superior to 3,5-bis(trifluoromethyl)phenylboronic acid (1) for the amide condensation of sterically demanding carboxylic acids. In contrast, 4c, which is prepared from a 1:2 molar mixture of B(OH)(3) and tetrachlorocatechol, is effective as a Lewis acid-assisted Br?nsted acid (LBA) catalyst for Ritter reaction.     

Synthesis and biological activities of novel furo[2,3,4-jk][2]benzazepin-4(3H)-one derivatives

A novel seven-membered lactam formation method has been established by intramolecular ring closure reaction of 4-bromo-(E)-3-[(2-alkylvinyl)carbonylamino]benzo[b]furans under Heck coupling conditions. A number of furo[2,3,4-jk][2]benzazepin-4(3H)-ones, tricyclicbenzo[b]furans, have been prepared by this method and evaluated for their leukotriene B(4) (LTB(4)) receptor and poly(ADP-ribose)polymerase-1 (PARP-1) inhibitory activities.     

Syntheses of biologically active natural products and leading compounds for new pharmaceuticals employing effective construction of a polycyclic skeleton

Cascade reactions are useful methods for the construction of polycyclic skeletons, which are important cores for biological activities. A variety of cascade reactions carried out under multiple reaction conditions, such as pericyclic, polar, radical, and transition metal-catalyzed reaction conditions, have been investigated. Culmorin, pentalenene, pentalenic acid, deoxypentalenic acid, longiborneol, cedrandiol, 8,14-cedranoxide, atisirene, atisine, and estrane-type steroids were synthesized via the intramolecular double Michael reaction. Aza double Michael reaction was applied to the syntheses of tylophorine, epilupinine, tacamonine, and paroxetine. Furthermore, sequential Michael and aldol reactions were performed in both intramolecular and intermolecular manners, leading to the formation of polycyclic compounds fused to a four-membered ring. Synthesis of paesslerin A utilizing a multicomponent cascade reaction revealed an error in the proposed structure. Unique cascade reactions carried out under radical and transition metal-catalyzed reaction conditions were also investigated. With the combination of several cascade reactions, serofendic acids and methyl 7beta-hydroxykaurenoate, both of which have neuroprotective activity, were synthesized in a selective manner.     

Cationic Rh complexes with novel spiro tetraarylpentaborate anions prepared from arylboronic acids and aryloxorhodium complexes

Ar-B(OH)2 (1a: Ar = C6H4OMe-4, 1b: Ar = C6H3Me2-2,6) react immediately with Rh(OC6H4Me-4)(PMe3)3 (2) in 5 : 1 molar ratio at room temperature to generate [Rh(PMe3)4]+[B5O6Ar4]- (3a: Ar = C6H4OMe-4, 3b: Ar = C6H3Me2-2,6). p-Cresol (92%/Rh), anisole (80%/Rh) and H2O (364%/Rh) are formed from 1a and 2. The reaction of 1a with 2 for 24 h produces [Rh(PMe3)4]+[B5O6(OH)4]- (4) as a yellow solid. This is attributed to hydrolytic dearylation of once formed 3a because the direct reaction of 3a with excess H2O forms 4. An equimolar reaction of 2 with phenylboroxine (PhBO)3 causes transfer of the 4-methylphenoxo ligand from rhodium to boron to produce [Rh(PMe3)4]+[B3O3Ph3(OC6H4Me-4)]- (5). Arylboronic acids 1a and 1b react with Rh(OC6H4Me-4)(PR3)3 (6: R = Et, 8: R = Ph) and with Rh(OC6H4Me-4)(cod)(PR3) (11: R = iPr, 12: R = Ph) to form [Rh(PR3)4]+[B5O6Ar4]- (7a: R = Et, Ar = C6H4OMe-4, 7b: R = Et, Ar = C6H3Me2-2,6, 9a: R = Ph, Ar = C6H3Me2-2,6) and [Rh(cod)(PR3)(L)]+[B5O6Ar4]- (13b: R = iPr, L = acetone, Ar = C6H3Me2-2,6, 14a: R = Ph, L = PPh3, Ar = C6H4OMe-4, 14b: R = Ph, L = PPh3, Ar = C6H3Me2-2,6), respectively. Hydrolysis of 14a yields [Rh(cod)(PPh3)2]+[B5O6(OH)4]- (15) quantitatively.     

Spiculoic acids A and B, new polyketides isolated from the Caribbean marine sponge Plakortis angulospiculatus

[structure: see text] Two novel polyketides, spiculoic acids A (1) and B (2), have been isolated from extracts of the Caribbean marine sponge Plakortisangulospiculatus. The structures of 1 and 2 were elucidated by detailed analysis of spectroscopic data. Spiculoic acid A (1) showed in vitro cytotoxicity against human breast cancer MCF-7 cells. It has a putative polyketide biogenetic origin that involves incorporation of four butyrate units and a Diels Alderase catalyzed intramolecular [4 + 2] cycloaddition reaction.     

2- und 6-Methyl-8-oxa-bicyclo[5.1.0]octa-2,4-dien. Über den Verlauf der Ringöffnung bei der Thermolyse in der Gasphase

2- and 6-Methyl-8-oxabicyclo[5.1.0]octa-2,4-diene. Ring cleavage reaction upon flash pyrolysis. 6-Methyl-8-oxa-bicyclo[5.1.0]-octa-2,4-diene ( 1 a ) has been subjected to flash pyrolysis with the aim to elucidate the course of its thermal ring cleavage reaction. At 100° equilibrium between 1a (6%) and its 2-methylisomer 1 b (94%) is reached through a remarkably facile [1,5]-hydrogen shift. Above 200° methyl-bicyclo[3.2.0]hept-2-ene-7-ones ( 3 ), dihydrotolualdehydes 5 and 6 and their aromatization products 7 are isolated. It is concluded that these products arise from 2-, 3- and 7-methyl-hepta-2,4,6-trienal 2a , 2b and 2f which are formed from 1a/1b by path C and D in Scheme 2 involving a formal [2+6]-cycloreversion reaction of 1a/1b and of its valence isomer, 1,2-homooxepine 11 . Two alternate pathways, A and B, involving cleavage of the C,C bond common to both rings in 1 concomitant or followed by hydrogen shifts are not operative.     

Synthesis and rearrangements of aminosubstituted ferra- and ruthenatricarbaboranes

A room-temperature reaction between the [7-tBuNH-nido-7,8,9-C3B8H10]- anion (1a) and [Cp*RuCl]4 leads to the ruthenatricarbollide [1-Cp*-12-tBuNH-1,2,4,12-RuC3B8H10] (2) (yield 85%). Analogously, the room-temperature photochemical reaction of 1a with [CpFe(C6H6)]PF6 gives the previously reported iron complex [1-Cp-12-tBuNH-1,2,4,12-FeC3B8H10] (3) (yield 82%). Both reactions are associated with extensive polyhedral rearrangement, which occurs under very mild conditions and brings the carbon atoms to positions of maximum separation within the framework. Compounds 2 and 3 were also surprisingly obtained via complexation of the isomeric [8-tBuNH-nido-7,8,9-C3B8H10]- (1b) anion. Complex 2 rearranges further to [1-Cp*-10-tBuNH-1,2,4,10-RuC3B8H10] (4) upon refluxing in xylene (145 degrees C). Density functional theory calculations at the B3LYP/SDD level were used to estimate relative stabilities of these metallacarborane isomers. Compounds 2 and 4, along with the 11-vertex closo compounds [1-Cp*-1,2,3,10-RuC3B7H10] (5) and [1-Cp*-10-tBuNH-1,2,3,10-RuC3B7H9] (6), were also isolated from the reaction between [Cp*RuCl2]2 and 1a in boiling xylene. The structure of 2 was established by an X-ray diffraction study, and the constitution of all compounds was determined unambiguously by multinuclear NMR spectroscopy, mass spectrometry, and elemental analyses.     

Ring-opening protonolysis of sila[1]ferrocenophanes as a route to stabilized silylium ions

The ring-opening reactions of a series of sila[1]ferrocenophanes with protic acids of anions with various degrees of noncoordinating character have been explored. Ferrocenyl-substituted silyl triflates FcSiMe2OTf (5 a) and Fc(3)SiOTf (5 b) (Fc=(eta5-C5H4)Fe(eta5-C5H5)) were synthesized by means of HOTf-induced ring-opening protonolysis of strained sila[1]ferrocenophanes fcSiMe2 (3 a) and fcSiFc2 (3 b) (fc=(eta5-C5H4)2Fe). Reaction of 3 a and 3 b with HBF4 yielded fluorosubstituted ferrocenylsilanes FcSiMe2F (6 a) and Fc3SiF (6 b) and suggested the intermediacy of a highly reactive silylium ion capable of abstracting F- from the [BF4]- ion. Generation of the solvated silylium ions [FcSiMe2THF]+ (7a+), [Fc3SiTHF]+ (7b+) and [FcSiiPr2OEt2]+ (7c+) at low temperatures, by reaction of the corresponding sila[1]ferrocenophanes (3 a, 3 b, and fcSiiPr2 (3 c), respectively) with H(OEt2)(S)TFPB (S=Et2O or THF; TFPB=tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) was monitored by using low-temperature 1H, 13C, and 29Si NMR spectroscopy. In situ reaction of 7a+, 7b+, and 7c+ with excess pyridine generated [FcSiMe2py]+ (8a+), [Fc3Sipy]+ (8b+), and [FcSiiPr2py]+ (8c+), respectively, as observed by 1H, 13C, and 29Si NMR spectroscopy. A preparative-scale reaction of 3 b with H(OEt2)(THF)TFPB at -60 degrees C and subsequent addition of excess pyridine gave isolable red crystals of 8b-[TFPB]CHCl3, which were characterized by 1H and 29Si NMR spectroscopy as well as by single-crystal X-ray diffraction.     

Investigation of naphthyridines. VII. Synthesis of 10-alkylamino-1,2,3,4-tetrahydrobenzo[b]-1,6-naphthyridines

10-Alkylamino-2-methy1-1,2,3,4-tetrahydrobenzo[b]-1,6-naphthyridines were obtained by cyclization of alkylamides of N-(1-methyl-4-piperidylidene)anthranilic acids and also by reaction of 10-chloro-2-methyl-1,2,3,4-tetrahydrobenzo-[b]-1,6-naphthyridines with amine hydrochlorides.See [1] for communication VI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 263–265, February, 1976.     

Synthesis of isoindolo[2,1-a]quinoline derivatives and their effects on N2-induced hypoxia

A variety of isoindolo[2,1-a]quinoline derivatives as well as the following related heterocycles have been prepared: 11b,12-dihydro-5H-isoindolo[2,1-b][2]benzazepine-7,13-dione (8a), 7,8,14,14a-tetrahydroisoindolo[2,1-c][3]benzazocine-5, 13-dione (8b), 6a,7-dihydroisoquinolino[2,3-a]quinoline-5,12-dione (12), 2,3,3a-4-tetrahydropyrrolo[1,2-a]quinoline-1,5-dione (14), and pyrido[2',3':3,4]pyrrolo[1,2-a]quinoline-5,11(5H)-dione (17). The key synthetic step involves an intramolecular Friedel-Crafts reaction of acid chlorides such as isoindole-1-acetyl chlorides (4), the acids (3) of which were prepared starting with 2-arylisoindole-1,3(2H)-diones (2-arylphthalimides) (1). The protective effects of isoindolo[2,1-a]quinoline derivatives (19 and 20) against N2-induced hypoxia were examined. Among them, 6-(diethylaminomethyl)isoindolo[2,1-a]quinoline-5,11(5H)-dio ne (19b) showed the most potency.     

Anomalous nucleosides and related compounds

In order to obtain nontoxic biologically active aza analogs of pyrimidine, the synthesis of amino acid derivatives of 6-azauracil has been carried out: a) by the reaction of 5-bromo-6-azauracil (I) [1] with amino acid salts, and b) by the carbodiimide condensation of 5-amino-6-azauracil (II) [1] with benzyloxycarbonylamino acids.     

Selective ring-opening reactions of

The reactivity of strained [1]ferrocenophanes, [Fe(eta-C5H4)2ERx] (ERx = SiMe2, 1a: SiMePh, 1b; SnR2, 1c), towards boron halides has been investigated and has been shown to provide a facile pathway to ferrocene derivatives functionalized with Lewis acidic boron centers. The boron halides RBX2 (R = Cl, Ph, fc; X = Cl, Br) (fc = Fe(eta-C5H4)2) lead to selective cleavage of the Si-Cp bonds in 1a and 1b to give, depending on the reaction stoichiometry, functionalized mono- or diferrocenylboranes RnB [(eta-C5H4)Fe(eta-C5H4SiMe2Cl)](3-n) (2a: R = Cl, n = 2; 2b: R = Cl, n = 1; 2c: R = Ph, n = 1) and RnB[(eta-C5H4)Fe(eta-C5H4SiMePhCl)](3-n) (2d: R = Cl, n = 2) in high yields. Compounds 2a-d were characterized by multinuclear NMR spectroscopy, mass spectrometry, and by single-crystal X-ray diffraction (for 2b). Most likely due to steric constraints, a triferrocenylborane was not obtained even from the reaction of BCl3 with an excess of 1a, whereas facile formation of the diferrocenylphenylborane 2c from PhBCl2 and two equivalents of 1a was observed. Selective hydrolysis of the B-Cl bonds of chlorodiferrocenylborane 2b in the presence of trace amounts of water led to the silylated tetranuclear ferrocene complex [(ClMe2Sifc)2B-O-B(fcSiMe2Cl)2] (3) without cleavage of the Si-Cl bonds. The structure of 3 was confirmed by an X-ray diffraction study. Studies of the reactivity of the higher Group 14 homologue of 1a and 1b, the tin-bridged [1]ferrocenophane 1c, revealed that facile addition of B-Cl bonds occurs across the Sn-Cp bonds to yield the 1-stannyl-1'-borylferrocenes [(ClMes2Sn)fc(BClR)] (4a: R = Cl; 4b: R = Ph; Mes = 2,4,6-Me3C6H2). The new synthetic methodology can be extended to bifunctional Lewis acids such as the bis(boryl)ferrocene 1,1'-fc(BBr2)2, which affords the linear boron-bridged ferrocene trimer 1,1'-[fc[B(Br)fcSiMe2Br]2] 5 in 54% isolated yield. In order to incorporate the functionalized ferrocenylboranes into polymer structures, compound 2c was reduced with Li[BEt3H] to give the silicon-hydride functionalized species [PhB[(eta-C5H4)Fe(eta-C5H4SiMe2H)]2] (6), which was then used as a capping reagent in the transition metal catalyzed polymerization of 1a. This process leads to the incorporation of the ferrocenylborane unit into the main chain of a poly(ferrocenylsilane) to afford [PhB-[(fcSiMe2)(n-1)fcSiMe2H]2] (7).     

Synthetic studies on diuretics. 5-(3,3-N,S-substituted-2-propenoyl)-2,3-dihydro-2- benzo[b]furancarboxylic acids

6,7-Dichloro-2,3-dihydro-2-benzo[b]furancarboxylic acid derivatives having a 3,3-N,S-disubstituted-2-propenoyl group at the 5-position were prepared by alkylation of 5-(thiocarbamoyl)acetyl derivatives of the 2,3-dihydro-2-benzo[b]furancarboxylic acid ester or by acetal exchange reaction of 5-[3,3-bis(alkylthio)-2-propenoyl] derivatives. Synthesis of 5-[4 and/or 5-(di)substituted-4-thiazolin-2-ylidene]acetyl-2,3- dihydro-2-benzo[b]furancarboxylic acids was also achieved by the reaction of 2-halo-1-methoxyethyl isothiocyanate with the 5-acetyl derivative in the presence of base or through sulfide contraction of 2-[[6,7-dichloro-2-methoxycarbonyl-2,3-dihydrobenzo[b]furan-5-yl) carbonyl)-methylthio]thiazolium bromide. Some of the compounds which were synthesized showed potent natriuretic activities in rats and mice. The structure-activity relationship is also discussed.     

Coordination of Lewis acid to eta(2)-enonepalladium(0) leading to continuous structure variation from eta(2)-olefin type to eta(3)-allyl type.

The reaction of alpha,beta-unsaturated carbonyl compounds, a palladium(0) complex, and Lewis acids led to the formation of a new class of complexes showing a wide variety of structures with eta(2)-type and eta(3)-type coordination of the carbonyl compounds. The reaction of Pd(PhCH=CHCOCH(3))(PPh(3))(2) with BF(3).OEt(2) or B(C(6)F(5))(3) quantitatively gave palladium complexes 1a,b having BX(3)-coordinated eta(2)-enonepalladium structure, as revealed by X-ray structure analysis of the B(C(6)F(5))(3) adduct 1b. On the other hand, the reaction of Pd(PhCH=CHCHO)(PPh(3))(2) with BF(3).OEt(2) or B(C(6)F(5))(3) gave distorted zwitterionic eta(3)-allylpalladium complexes 3a,b, where the Pd-carbonyl carbon distance in 3a (2.413(4) A) is much shorter than that (2.96(1) A) in 1b. The values of the P-P coupling constant and (13)C chemical shift for carbonyl carbon are useful criteria for predicting how the eta(3)-coordination mode contributes to the structure of the enone-palladium-Lewis acid system. Molecular orbital calculations on the series of model complexes suggest that orbital overlap in the highest occupied molecular orbital between the palladium and carbonyl carbon is enlarged by coordination of the Lewis acid to the carbonyl group. Palladium-catalyzed conjugate addition of R-M (R-M = AlMe(3), AlEt(3), ZnEt(2)) and its plausible reaction path are also reported.     

Synthesis of HKI 0231B

[reaction: see text] The total synthesis of HKI 0231B (1b) was completed in 12 linear steps and 15.6% overall yield. An unusual anionic cyclization provided access to intermediate 61 and the embedded benz[cd]indol-3-(1H)-one ring system 3. Directed ortho-lithiation in the presence of a ketone followed by formylation and finally acid-catalyzed methanolysis complete the synthesis. Studies directed toward the construction and reactivity of the lactam acetal functionality present in HKI 0231A (1a) are also reported.     

The first regioselective metalation and functionalization of unprotected 4-halobenzoic acids

[reaction: see text] By treatment with s-BuLi, s-BuLi/TMEDA, or t-BuLi at approximately -78 degrees C, 4-fluoro- and 4-chlorobenzoic acids (1a,b) are metalated preferentially in the position adjacent to the carboxylate. A complete reversal in regioselectivity is observed for 1a when treated with LTMP; a sequential process involving a rapid intraaggregate lithiation through a quasi dianion complex "QUADAC" is postulated to explain the unusual reactivity of Me(2)S(2) and I(2).     

Bidentates versus monodentates in asymmetric hydrogenation catalysis: synergic effects on rate and allosteric effects on enantioselectivity

C 1-Symmetric phosphino/phosphonite ligands are prepared by the reactions of Ph 2P(CH 2) 2P(NMe 2) 2 with ( S)-1,1'-bi-2-naphthol (to give L A ) or ( S)-10,10'-bi-9-phenanthrol (to give L B ). Racemic 10,10'-bi-9-phenanthrol is synthesized in three steps from phenanthrene in 44% overall yield. The complexes [PdCl 2( L A,B )] ( 1a, b), [PtCl 2( L A,B )] ( 2a, b), [Rh(cod)( L A,B )]BF 4 ( 3a, b) and [Rh( L A,B ) 2]BF 4 ( 4a, b) are reported and the crystal structure of 1a has been determined. A (31)P NMR study shows that M, a 1:1 mixture of the monodentates, PMePh 2 and methyl monophosphonite L 1a (based on ( S)-1,1 '-bi-2-naphthol), reacts with 1 equiv of [Rh(cod) 2]BF 4 to give the heteroligand complex [Rh(cod)(PMePh 2)( L 1a )]BF 4 ( 5) and homoligand complexes [Rh(cod)(PMePh 2) 2]BF 4 ( 6) and [Rh(cod)( L 1a ) 2]BF 4 ( 7) in the ratio 2:1:1. The same mixture of 5- 7 is obtained upon mixing the isolated homoligand complexes 6 and 7 although the equilibrium is only established rapidly in the presence of an excess of PMePh 2. The predominant species 5 is a monodentate ligand complex analogue of the chelate 3a. When the mixture of 5- 7 is exposed to 5 atm H 2 for 1 h (the conditions used for catalyst preactivation in the asymmetric hydrogenation studies), the products are identified as the solvento species [Rh(PMePh 2)( L 1a )(S) 2]BF 4 ( 5'), [Rh(S) 2(PMePh 2) 2]BF 4 ( 6') and [Rh(S) 2( L 1a ) 2]BF 4 ( 7') and are formed in the same 2:1:1 ratio. The reaction of M with 0.5 equiv of [Rh(cod) 2]BF 4 gives exclusively the heteroligand complex cis-[Rh(PMePh 2) 2( L 1a ) 2]BF 4 ( 8), an analogue of 4a. The asymmetric hydrogenation of dehydroamino acid derivatives catalyzed by 3a, b is reported, and the enantioselectivities are compared with those obtained with (a) chelate catalysts derived from analogous diphosphonite ligands L 2a and L 2b , (b) catalysts based on methyl monophosphonites L 1a and L 1b , and (c) catalysts derived from mixture M. For the cinnamate and acrylate substrates studied, the catalysts derived from the phosphino/phosphonite bidentates L A,B generally give superior enantioselectivities to the analogous diphosphonites L 2a and L 2b ; these results are rationalized in terms of delta/lambda-chelate conformations and allosteric effects of the substrates. The rate of hydrogenation of acrylate substrate A with heterochelate 3a is significantly faster than with the homochelate analogues [Rh( L 2a )(cod)]BF 4 and [Rh(dppe)(cod)]BF 4. A synergic effect on the rate is also observed with the monodentate analogues: the rate of hydrogenation with the mixture containing predominantly heteroligand complex 5 is faster than with the monophosphine complex 6 or monophosphonite complex 7. Thus the hydrogenation catalysis carried out with M and [Rh(cod) 2]BF 4 is controlled by the dominant and most efficient heteroligand complex 5. In this study, the heterodiphos chelate 3a is shown to be more efficient and gives the opposite sense of optical induction to the heteromonophos analogue 5.     

The adenine ring influences the adenosine 5′-triphosphate hydrolysis

DFT calculations (ωB97X-D) of the adenosine 5′-triphosphate (ATP) hydrolysis were carried out. Four reactions (A), (B), (C), and (D) were investigated. Reaction (A) is of the acid catalysis and (B) is of the Mg²⁺ one with (H₂O) _n, n = 5, 11, and 17. (C) is of the myosin-model catalysis, and (D) is of the F₁-ATPase one. Transition states were determined precisely. For reaction (A), the experimental activation energy was reproduced well by the n = 11 and 17 models. For the Mg²⁺-containing hydrolysis, (B), 2 reactions (a) [without the Mg²⁺-adenine linkage] and (b) [with the connection] were examined and were compared. The reaction (b) was found to be more likely than (a) in both total and activation energies. The adenine ring works to enhance the polarity of transition states. For the myosin catalyzed (C) and in F₁-ATPase (D) hydrolyses, again, the reaction (b) is much more likely than (a). The proton transfer from the lytic water molecule leads to the protonation of the carboxylate of Glu459 in (C). The adenine ring was suggested to influence and promote the ATP hydrolysis.     

Binding of amino acids into a novel multiresponsive ferrocene receptor having an ene backbone

[reaction: see text] Receptor 1 featuring two open arms, multipoint binding sites, and unsaturated linkers on a ferrocene platform shows strong 1:1 binding to unprotected alpha-amino acids (UV-vis, fluorescence, CV, ITC, NMR, and ESI-MS). NMR and ESI-MS studies suggest an encapsulative binding mode involving the alpha,beta-unsaturated carbonyl residue (site for -NH3+, interaction A) and the terminal -OH groups (site for -COO-, interaction B).     

Intramolecular Borylation via Sequential B−Mes Bond Cleavage for the Divergent Synthesis of B,N,B‐Doped Benzo[4]helicenes

New symmetric and unsymmetric B,N,B‐doped benzo[4]helicenes 3 – 6 a/b have been achieved in good yields, using a three‐step process, starting from N(tolyl)₃ in a highly divergent manner (7 examples). A borinic acid functionalized 1,4‐B,N‐anthracene 1 was found to display unprecedented reactivity, acting as a convenient and highly effective precursor for selective formation of bromo‐substituted B,N,B‐benzo[4]helicenes 2 a / 2 b via intramolecular borylation and sequential B?Mes bond cleavage in the presence of BBr₃. Subsequent reaction of 2 a / 2 b with Ar‐Li provided a highly effective toolbox for the preparation of symmetrically/unsymmetrically functionalized B,N,B‐helicenes. Their high photoluminescence quantum yields along with the small ΔE_ST suggest their potential as thermally activated delayed fluorescence (TADF) emitters for organic light‐emitting diodes (OLEDs).