Neutral Fischer carbene complexes bearing alkoxy groups as the donor substituents on the carbene carbon atom have been synthesized by direct alkylation of the lithium acylmetalates (formed by classical addition of organolithium compounds to metal hexacarbonyl) by alkyl iodides. It was shown that the reaction proceeds under normal phase-transfer conditions (CH2-Cl2/H2O) or, preferably, in aqueous medium alone. However, in both cases the presence of a catalytic amount of a tetraalkylammonium salt (n-Bu4NBr) was required. Attractive features of this methodology are (i) the economy of using alkyl iodides in place of the usual alkylating agents (like Me3O+BF4-, magic methyl, or methyl triflate), (ii) the procedural ease of ''one-pot'' preparation of the carbene complexes, and (iii) the greater variety of alkyl moieties that can be incorporated as part of the alkoxy substituent using the more readily available alkyl iodides containing nontrivial alkyl groups. The procedure is preparatively useful for accessing chromium-containing carbenes, but yields of the analogous molybdenum- and tungsten-containing species are only less-than-or-equal-to 10%. Mechanistic considerations suggest that products are formed by competing pathways involving direct S(N)2 displacement vs electron-transfer-initiated S(RN)1 processes.
Dihydropyridines in Organometallic Synthesis. Formation of Pyridine and Dihydropyridine-Stabilized Alkylidene Complexes of Tungsten(0) and Chromium(0) from Fischer Carbene Complexes: Structure and Reactivity
1,2- and 1,4-dihydropyridines react with alkoxycarbene complexes of chromium and tungsten to give, upon an unprecedented hydride transfer, alcohol elimination, and pyridine fixation on the carbene carbon, a new class of air-stable pyridinium ylide complexes. These pyridine-protected alkylidene complexes of chromium(0) and tungsten(0) were fully characterized by X-ray crystallography. In the case of
Fischer Dinuclear and Mononuclear Bis-Carbene Complexes of Thiophene and Thiophene Derivatives
作者:Simon Lotz、Nina A. van Jaarsveld、David C. Liles、Chantelle Crause、Helmar Görls、Yvette M. Terblans
DOI:10.1021/om300414y
日期:2012.8.13
The reaction of dilithiated thiophene and thiophene derivatives with group 6 transition metal carbonyl precursors and subsequent alkylation afforded linearly arranged Fischer 2,5-bis-carbene and the rare unsymmetrical 2,3-bis-carbene chelated complexes. The latter requires a second lithiation to occur at an adjacent, less reactive site on the thiophene ring. The control of reactivity sites was investigated
Organic Syntheses via Transition-Metal Complexes. 119.<sup>1</sup> α-Methylenation and α-Alkenylation of α,β-Unsaturated Amides by Means of Carbene Tungsten Complexes: A Novel Baylis−Hillman Type Reaction
Fischer carbene complexes were found to undergo Baylis−Hillman type additions to α,β-unsaturated acidamides. Reactions of (non-CH-acidic) carbene tungsten complexes 1a−c with (CH-acidic) but-2-enoic acidamides 2 in the presence of POCl3/Et3N resulted in an α-addition of the carbene ligand to the amide backbone and formation of cross-conjugated aminocarbenecomplexes 3. Reaction of CH-acidic carbene
发现费歇尔卡宾络合物在α,β-不饱和酰胺中经历了Baylis-Hillman类型的加成反应。在POCl 3 / Et 3 N存在下,(非CH酸性)卡宾钨配合物1a - c与(CH酸性)丁-2-烯酰胺2的反应导致卡宾配体的α加成反应酰胺主链和交叉共轭氨基卡宾配合物的形成3。CH的反应-酸性卡宾络合物钨1D - ħ得到交叉共轭aminocarbene络合物9(其是这样的化合物的双键异构体3)与(环丁烯基)卡宾配合物10分别通过α-和β加成到丁-2-烯酰胺2上。化合物9和10是化合价异构体,但它们不会发生热互变。
Organic Syntheses via Transition Metal Complexes. 116.<sup>1</sup> Carbocyclic Four-, Five-, and Six-Membered Rings by Condensation of (Alkyl,ethoxy)carbene Complexes (M = W, Cr) with α,β-Unsaturated Tertiary Acid Amides
(cyclohexan-4-on-1-yl)carbene tungsten complexes 6 were obtained by condensation of (ethoxy,methyl)carbene tungsten complex (OC)5WC(OEt)CH3 1a with α,β-unsaturated tertiary acid amides PhCHCHC(O)NR2 7 in the presence of POCl3/Et3N and (COCl)2/Et3N, respectively. Compounds 2 underwent a π-cyclization to zwitterionic η1-cyclopentadiene complexes 3. Condensation of (prim-alkyl,ethoxy)carbenecomplexes (CO)5MC(OEt)CH2R1
4-氨基-1-钨-1,3,5-己三烯(CO)5 W C(OEt)CH C(NR 2)CH CHPh(3 E)-2和(环己基4-on-1-基)卡宾钨配合物6是通过在(乙氧基,甲基)卡宾钨配合物(OC)5 W C(OEt)CH 3 1a与α,β-不饱和叔酰胺PhCh CHC(O)NR 2 7的缩合反应中获得的。将POCl 3 / ET 3 N和(氯化钴)2 / ET 3 N,分别。化合物2经历了π-环化,两性离子η 1-环戊二烯配合物3。的缩合(整洁-烷基,乙氧基)卡宾配合物(CO)5中号C(OET)CH 2 - [R 1 1(M = W,铬; R 1 = C ^ -C 7 ħ 7,Ñ -Pr)用化合物7,得到(环丁烯基)卡宾络合物9。
Strikingly Different Reactivity Patterns of Fischer Alkoxycarbene and Thiocarbene Complexes in Experimental and Theoretical Studies
complexes 11a−l, derived from [(OC)5MC(SEt)CH2R] (8a−e; M = W, Cr; R = n-Pr, Me, c-C7H7, c-C6H7Fe(CO)3) and imidoyl chlorides under similar conditions, form pyrroles 16a−h and 17k,l by α-cyclization. On the basis of the calculated DFT/BP86 potential energy surfaces of the particular reaction channels it is shown that (β-imino)alkoxycarbene compounds 10 prefer a metalla(di-π-methane) rearrangement due to
观察到铬和钨的烷氧基卡宾和硫代卡宾络合物的反应存在显着差异。因此,由[(OC)5 W C(OEt)CH 2 R](7a - c ; R = n -Pr,Me,c -C 7 H 7原位生成(β-亚氨基)乙氧基卡宾络合物10a - e)和亚氨酰氯R 1 ClC NCHR 2 R 3(9a - f ; R 1 = t- Bu,Ph,2-呋喃基; R 2 = H,Me; R 3= Me,Et,Ph),经历了金属(二-π-甲烷)重排,生成(N-烯氨基)乙氧基卡宾络合物12a - e,而相应的(β-亚氨基)硫代卡宾络合物11a - l衍生自[(OC )5 M C(SEt)CH 2 R](8a - e ; M = W,Cr; R = n -Pr,Me,c -C 7 H 7,c -C 6 H 7 Fe(CO)3)和亚氨酰氯在相似条件下形成吡咯16a - h和通过α-环化得到的17k,l。具体的反应通道的计算DFT