Cyclopropyl complex

Most of the SO2 reactions presented in this section, especially those of the propargyl and cyclopropyl complexes, contrast sharply with the reactions of the corresponding tin-carbon compounds. Representative examples of the latter are provided in Eqs. (28)-(30) (49, SO). It is... 

A series of complexes of the general structure 102 has been studied. For the cyclobutyl, cyclopentyl, and cyclohexyl derivatives, crystallographic and NMR data showed a-agostic interactions. In sharp contrast, the cyclopropyl complex showed no sign of C-H agostic interactions. Instead, an unusual a-agostic C-C interaction was detected. ... 

The last member of the family [NbCl(Tp )(c-CnH2n-i)] (n = 3-6) has been also recently reported [NbCl(c-C4H7)(Tp )(MeC=CMe)] is similar to cyclopentyl and cyclohexyl analogues, and very different from the cyclopropyl derivatives. The cyclobutyl complex exhibits an a-C-H agostic interaction in the dominant isomer, with no evidence for the a-C-C agostic character found for the smaller ring that seems to be unique for the cyclopropyl complex.41... 

Thus it converts the cyclopropyl complex FPCHCH2CH2 or the cyclopropylmethyl... 

A curious reactivity of the cyclopropyl complex 397 is its tendency, under ambient conditions, to rearrange intramolecularly to afford the rhodacyclobutane complex 154 (ri/2 = 95min). In turn, 154 rearranges thermally to the f/ -propene complex 153, which upon prolonged heating in loses propene to afford... 

T-cyclopropyl complex rro j-[Pt(CHCHaCH2)Cl(PMe2Ph)2] with AgNO, followed by treatment with KPFe, yields the analogous [( -allyl)Pt(PMe2Ph8]+... 

Since Evans s initial report, several chiral Lewis acids with copper as the central metal have been reported. Davies et al. and Ghosh et al. independently developed a bis(oxazoline) ligand prepared from aminoindanol, and applied the copper complex of this ligand to the asymmetric Diels-Alder reaction. Davies varied the link between the two oxazolines and found that cyclopropyl is the best connector (see catalyst 26), giving the cycloadduct of acryloyloxazolidinone and cyclopentadiene in high optical purity (98.4% ee) [35] (Scheme 1.45). Ghosh et al., on the other hand, obtained the same cycloadduct in 99% ee by the use of unsubstituted ligand (see catalyst 27) [36] (Scheme 1.46, Table 1.19). 

The addition of carbene to a 3-(halopropyl)-5//-dibenz[7>./]azepine 5 (X = Cl, Br) in a Simmons—Smith reaction is more complex and results in a mixture of the tetracycle 6 (6%), its cyclopropano derivative 7 (48 %), the 5-allyl derivative 8 and the (cyclopropyl)methyl compound 9, the latter two products in a combined yield of 12%.31... 

In this way benzalaniline reacts with dimsyl anion to give /J-anilinosulphoxide 446 in 92% yield401 (equation 267). Nudelman and Cram have found that the analogous reaction with the carbanion of benzyl p-tolyl sulphoxide is more complex and leads to the formation of substituted cyclopropyl sulphoxides 447 (equation 268)522. The carbanion derived from cyclohexanone dimethyldithioacetal S-oxide 448 gives /J-mercaptoanilines derivatives on treatment with iminoketones and further elaboration523 (equation 269). 

An analogous cyclization to eventually form five-membered rings has also been observed for l-metalla-l,3,5-hexatrienes with an additional heteroatom within the chain, such as in the complexes 157. These are obtained by Michael additions of imines to alkynylcarbene complexes in good to excellent yields (reaction type F in Scheme 4), and their configurations were determined to be Z (>91%) in all cases. Upon warming in THF solution, complexes 157 underwent cyclization with reductive elimination to furnish 2Ff-pyrroles 158 in up to 97% yield (Scheme 34). With two cyclopropyl substituents at the terminus in... 

Other examples of [2C+2S+1C0] cycloaddition reactions have been described by Herndon et al. by the use of chromium cyclopropyl(methoxy)carbenes. These complexes react with alkynes releasing ethene and forming cyclopenta-dienone derivatives, which evolve to cyclopentenone derivatives in the presence of chromium(O) and water [122] (Scheme 76). This reaction has been extended to intramolecular processes and also to the synthesis of some natural products [123]. These authors have also described another process involving a formal [2C+2S+1C0] cycloaddition reaction. Thus, the reaction of methyl and cyclo-propylcarbene complexes with phenylacetylene derivatives does not afford the expected benzannulated products, and several regioisomers of cyclopentenone derivatives are the only products isolated [124] (Scheme 76). 

Alkoxycarbene complexes with unsaturation in the alkyl side chain rather than the alkoxy chain underwent similar intramolecular photoreactions (Eqs. 10 and 11) [60]. Cyclopropyl carbene complexes underwent a facile vinyl-cyclopropane rearrangement, presumably from the metal-bound ketene intermediate (Eqs. 12 and 13) [61]. A cycloheptatriene carbene complex underwent a related [6+2] cycloaddition (Eq. 14) [62]. 

The complex [Fe(D4-TmAP)Cl] with Halterman s porphyrin ligand can effect asymmetric alkene cyclopropanation with diazoacetate in high product yield and high stereoselectivity [57]. The reaction occurs smoothly at room temperature without the need for addition of CoCp2, affording the cyclopropyl esters... 

Cyclopropyl ketones 32 and cyclopropyl imines 33 can also undergo [3+2] cycloaddition reactions with enones 34 in presence of NHC-Ni complexes to afford the corresponding cyclopentane compounds 35 (Scheme 5.9) [11]. The catalytic system is prepared in situ from the use of [Ni(COD),], SIPr HCl salt and KOBu, the reaction also required the use of Ti(O Bu) as an additive to improve yields and increase reactions rates. In most of the cases, th products 35 were obtained in good to excellent diastereoselectivities. 

Scheme 5.26 [4+2] cycloaddition reaction catalysed by golden-NHC complex between cyclopropyl ketones and enol ether... 

A reagent system that is selective for allylic, benzylic, and cyclopropyl alcohols uses iodosobenzene in conjunction with a Cr(III)(salen) complex.12... 

For methyl cyclopropyl ketone the question is more complex since in addition to the low-lying n and n levels, a cyclopropyl level is present also<89) ... 

The second large group of reactions is characterised by the elaboration of the exocyclic double bond. This chemistry is particularly interesting because it allows the incorporation of a cyclopropyl ring in a more complex molecule, to take advantage of its peculiar feature as a reactive three-carbon functional group. 

The photoindueed 1,7-cycloaddition of carbon monoxide across the divinyl-cyclopropane derivative 32 yields the two cyclic dienyl ketones 34, via the ferracyclononadiene intermediate 33 [18]. (Scheme 11) cyclopentene rearrangement. The dienylcyclopropane 35 is capable of forming the complex 36, followed by ring enlargement to 37 [19]. 1,1-Dicyclopropylethylene 29 is also converted to the 1-cyclopropyl-1-cyclopentene 38. The additional functionality of vinylcyclopropanes is necessary to serve as a 7t-donor... 

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