Synthesis of Rhenabenzenes from the Reactions of Rhenacyclobutadienes with Ethoxyethyne

Abstract

Treatment of Na[Re(CO)5 ] with RCCCO2 Et (R=phenyl, naphthalen-1-yl, phenanthren-9-yl and pyren-1-yl) followed by reaction with acetyl chloride and ethanol afforded the rhenacyclobutadienes Re{-C(R)C(CO2 Et)C(OEt)}(CO)4 . Reactions of these rhenacyclobutadienes with HCCOEt produced rhenabenzenes Re{-C(R)C(CO2 Et)C(OEt)CHC(OEt)}(CO)4 . Except for R=Ph, new rhenacyclobutadienes with pendant alkenyl substituents Re{-C(R)C(C(OEt)CH(CO2 Et))C(OEt)}(CO)4 were also isolated from these reactions. The NMR spectroscopic and X-ray structural data, as well as the aromatic stabilization energy (ASE) values suggest that the rhenabenzenes are aromatic, with extensive delocalized π character.

Rhenabenzenes and Unexpected Coupling Products from the Reactions of Rhenacyclobutadienes with Ethoxyethyne

“…1 H NMR (400.1 MHz, CD 3 CN): δ 1.56 (t, J = 6.8 Hz, 3H, OCH 2 CH 3 ), 3.08 (s, 3H, CO 2 CH 3 ), 4.08 (s, 3H, OCH 3 ), 4.51 (q, J = 6.8 Hz, 2H, OCH 2 CH 3 ), 6.31 (s, 1H, CH), 6.83 (d,J = 7.2 Hz,1H,Np),3H,Np),7.57 (d,J = 8.4 Hz, 1H, Np), 7.70 (d,J = 8.0 Hz,1H,Np),7.85 (d,J = 8.4 Hz,1H,Np). 13 C{ 1 H} NMR (100.6 MHz, CD 3 CN): δ 14.5 (s, OCH 2 CH 3 ), 51.3 (s, CO 2 CH 3 ), 58.6 (s, OCH 3 ), 70.0 (s, OCH 2 CH 3 ), 104.2 (s, CH), 117.9, 125.5, 125.6, 126.0, 126.6, 127.6, 127.8, 129.0, 134.4, by slowly evaporating the dichloromethane solvent from its saturated solution. The diffraction intensity data of 6, 8, 10, and 12 were collected with an Oxford Diffraction Gemini S Ultra X-ray Diffractometer with monochromatized Cu−K α radiation (λ = 1.54178 Å) at 100 K. Diffraction data were collected and processed using the CrysAlisPro software (version 1.171.35.19).…”

“…13 C{ 1 H} NMR (100.6 MHz, CD 3 COCD 3 ): δ 51.4 (s, CO 2 CH 3 ), 71. 8 (s,OCH 3 ),124.0,126.6,126.8,127.5,127.6,127.7,129.9,130.1,135.0,148.2 (all s,C of Np), 156.9 (s, C(CO 2 Me)), 160.2 (s, CO 2 Me), 192.0 (s, trans-Re(CO)), 193.1 (s, Re(CO)), 194.8 (s, Re(CO)), 230.5 (s, ReC(Np)), 249.6 (s, ReC(OMe)).…”

“…12 We have recently found that reactions of rhenacyclobutadienes 1 with HCCOEt produced a mixture of species, from which we were able to isolate two types of compounds, one is the rhenabenzene complexes 2 and the other one is the vinylsubstituted rhenacyclobutadiene complexes 3 (Scheme 2). 13 Complexes 2 are formed by formal insertion of HCCOEt into Re−C bonds, the mechanism of which has been described in detail in our previous report. 13 At first sight, complexes 3 can be thought as being formed by formal insertion of HCCOEt into the C-C(CO 2 Et) bonds of 1.…”

“…13 Complexes 2 are formed by formal insertion of HCCOEt into Re−C bonds, the mechanism of which has been described in detail in our previous report. 13 At first sight, complexes 3 can be thought as being formed by formal insertion of HCCOEt into the C-C(CO 2 Et) bonds of 1. The formation of 3 from the reaction of 1 with HCCOEt is somewhat surprising and unexpected, considering reactivities previously reported for metallacyclobutadiene complexes toward alkynes.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…Several . 638) in the presence of acetyl chloride [948]. The initially-produced alkoxycarbenes were converted the aminocarbene complexes (e.g.…”