Borabicyclo[3.2.0]heptadiene: A Fused Bicyclic Isomer of Borepin

Abstract

A new isomer of borepin, identified as 2-borabicyclo[3.2.0]hepta-3,6-diene by single-crystal X-ray diffraction and heteronuclear NMR spectroscopy, was obtained by reaction of 1-mesityl-2,3,4,5-tetraphenylborole with the diaminoalkyne bis(piperidyl)acetylene. Analogous reactions of the alkyne with other borole derivatives generated seven-membered borepins, in which a second equivalent of the alkyne was found to insert into the exocyclic B-C bond. Results of mechanistic DFT studies as well as differences in the reactivity of the boroles toward the diaminoalkyne are discussed.

Dimerisation of Dipiperidinoacetylene: Convenient Access to Tetraamino‐1,3‐Cyclobutadiene and Tetraamino‐1,2‐Cyclobutadiene Metal Complexes

“…[5] Compound 1 also reacted as av icinal dicarbenoid towards main-group Lewis acids such as BPhCl 2 ,w ith formation of ad iboranea dduct; [7] however,B ÀCb ond activation and 1,2-carboboration was found when BPh 3 or cyclic boroles such as 1-mesityl-2,3,4,5-tetraphenylborole wereu sed. [7,8] Similar reactivity was found for diboranea nd dialane species, which proceeded with diborationa nd dialumination of the CCtriplebond in 1. [9] Unprecedented reactivity was also observed upon reaction of 1 with the molybdenuma lkylidyne complex [MesCMo{OC-Me(CF 3 ) 2 } 3 ]( Mes = 2,4,6-trimethylphenyl), which afforded the paramagnetic metallacyclobutadiene (MCBD) complex V with a triplet ground state (S = 1) through cleavage of the carboncarbon triple bond and insertion of the alkylidyne moiety.…”

“…Unlike the coplanar orientation in the gold(I) and rhodium(I) complexes 5 and 6, the CBA ligand is tilted with regard to the metal atom as indicated by an W-C1-C3 angle of 158.40(16)8 (Table 2), presumably because of steric interaction with the sterically more de-mandingW (CO) 5 complex fragment;t he tungsten atom lies 0.91 out of the plane of the four-membered ring, which has am ean deviation of 0.05 ,s omewhat larger than in the other compounds presented here. The WÀC1 bond length is 2.319(3) ,w hich is slightly longer than usually found for [(NHC)W(CO) 5 ]c omplexes, for example 2.282(3) in [(ICy)W(CO) 5 ], [41] 2.275 (8) in [( Me IEt)W(CO) 5 ]( Me IEt = 1,3-diethyl- 4,5-dimethylimidazolin-2-ylidene), or 2.260(2) in [(IDipp)-W(CO) 5 ]. [42] The tungsten pentacarbonyl complex 7 was also investigated by IR spectroscopy.T he IR spectrum showsb ands for the four CO stretching modes ñ(CO) = 1866 (A 1 (1) ), 1888 (E), 1942 (B 1 ), 2047 (A 1…”

“…The diaminodicarbene character of 1 was also discovered by isolation of the homobimetallic complexes IV , whereas heterobimetallic Ru–Pd complexes were obtained by treatment of I with [(CH 3 CN) 2 PdCl 2 ] . Compound 1 also reacted as a vicinal dicarbenoid towards main‐group Lewis acids such as BPhCl 2 , with formation of a diborane adduct; however, B−C bond activation and 1,2‐carboboration was found when BPh 3 or cyclic boroles such as 1‐mesityl‐2,3,4,5‐tetraphenylborole were used . Similar reactivity was found for diborane and dialane species, which proceeded with diboration and dialumination of the C≡C triple bond in 1…”

Retracted: Facile synthesis of two oxocan derivatives using some chemical strategies

“…There are several studies for the synthesis of some bicyclo[3.2.0]heptadiene derivatives using some reagents such as Pd/C, [ 12 ] 7‐methoxycycloheptatriene, [ 13 ] aluminum chloride, [ 14 ] 1,2‐bis(piperidyl)acetyle, [ 15 ] and others. In this study, two bicyclo[3.2.0]heptadiene derivatives ( 2 and 4 ) were prepared via reaction of either imidazole or 2‐methylimidazole with acetonitrile to form either compounds 2 or 4 using Copper(II) chloride as catalyst (Scheme 1).…”

A Cationic NHC‐Supported Borole

“…A high‐field shifted 11 B NMR resonance at −11.4 ppm is in line with interactions of the Lewis‐acidic boron atom with an adjacent CC π‐bond as previously observed . Reactions of alkynes with boroles are known to form a series of products including Diels–Alder adducts, ring expanded borepins, or more complicated rearrangements, depending on the electronics and sterics of substituents …”