Relationships between the carbon-oxygen stretching frequencies of carboxylato complexes and the type of carboxylate coordination

In studying the evolution of organic chemistry and grasping its essence, one comes quickly to the conclusion that no other type of reaction plays as large a role in shaping this domain of science than carbon-carbon bond-forming reactions. The Grignard, Diels-Alder, and Wittig reactions are but three prominent examples of such processes, and are among those which have undeniably exercised decisive roles in the last century in the emergence of chemical synthesis as we know it today. In the last quarter of the 20th century, a new family of carbon-carbon bond-forming reactions based on transition-metal catalysts evolved as powerful tools in synthesis. Among them, the palladium-catalyzed cross-coupling reactions are the most prominent. In this Review, highlights of a number of selected syntheses are discussed. The examples chosen demonstrate the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.

Palladium-catalyzed cross-coupling reactions in total synthesis.

Sol-gel chemistry of transition metal oxides

The design and implementation of cascade reactions is a challenging facet of organic chemistry, yet one that can impart striking novelty, elegance, and efficiency to synthetic strategies. The application of cascade reactions to natural products synthesis represents a particularly demanding task, but the results can be both stunning and instructive. This Review highlights selected examples of cascade reactions in total synthesis, with particular emphasis on recent applications therein. The examples discussed herein illustrate the power of these processes in the construction of complex molecules and underscore their future potential in chemical synthesis.

Cascade reactions in total synthesis.

The Diels-Alder reaction has both enabled and shaped the art and science of total synthesis over the last few decades to an extent which, arguably, has yet to be eclipsed by any other transformation in the current synthetic repertoire. With myriad applications of this magnificent pericyclic reaction, often as a crucial element in elegant and programmed cascade sequences facilitating complex molecule construction, the Diels-Alder cycloaddition has afforded numerous and unparalleled solutions to a diverse range of synthetic puzzles provided by nature in the form of natural products. In celebration of the 100th anniversary of Alder's birth, selected examples of the awesome power of the reaction he helped to discover are discussed in this review in the context of total synthesis to illustrate its overall versatility and underscore its vast potential which has yet to be fully realized.

https://www.ch.ic.ac.uk/local/organic/pericyclic/DA.pdf

The Diels--Alder reaction in total synthesis.

The formation of a mixture of lactones as a minor product of the flash vacuum pyrolysis of diphenyl-methyl propiolate (1) has been investigated further. The diphenylfuran-2-ones (3), (4), and (5) are shown to be formed through an intramolecular insertion reaction of the methylenecarbene (2), formed from (1) at 640°, which leads to 5,5-diphenyl-furan-2(5H)- one (3) as the primary product. 3-Phenylphthalide (8) is apparently formed by intramolecular Diels-Alder addition of the C≡C bond of (1) to one phenyl ring which acts as the diene component, followed by loss of acetylene from an intermediate barrelene derivative (10). This is confirmed by a deuterium labelling experiment. 1-Phenyl-2-benzoxepin-3(1H)-one (7), considered at first as a possible intermediate in the pyrolysis of (1), is synthesized in six steps from 2-aminobenzophenone, and its X-ray structure determination is reported. On pyrolysis at 640°/0.07 mm (7) decarbonylates smoothly to give 2-vinylbenzophenone.

Methyleneketenes and methylenecarbenes. XVI. The formation of Diphenylfuran-2-ones and 3-Phenylphthalide as minor products of the pyrolysis of diphenylmethyl propiolate

From reactions between PtX2( deen ) (X=I, Br or Cl ; deen = N,N-diethylethane-1,2-diamine), thallous pentafluorobenzoate or 2,3,5,6-tetrafluorobenzoate, and the appropriate polyfluorobenzene in pyridine (py) or 4-methylpyridine ( mepy ), the organoamidoplatinum (II) complexes [Pt(NRCH2CH2Net2)X(L)](R = p-HC6F4 or C6F5, X = 1, Br or Cl , L = py; R = p-HC6F4, X = I, L = mepy ; R = p-MeC6F4 or p-IC6F4, X = I, L = py; R = 2,3,5-F3C6H2, X = Br, L = py) have been prepared. The X-ray crystal structure of [Pt(NC6F5CH2CH2Net2)I(py)](triclinic, space group Pī (No. 2), a 9.308(1), b 9.615(2), C 11.143(2)Ǻ, α 88.70(2),β 88.58(1), γ 89.60(2)°, R 0.0518, Rw 0.0704 for 3237 observed reflections) shows the complex to have square planar stereo-chemistry with py trans to NEt2 and NC6F5 trans to iodine. The stereochemistry of the amido nitrogen approaches triangular (sum of angles 353°) and the N-C6F5 bond has partial double-bond character. Surprisingly, the ethyl substituents have a configuration in which the methyl groups are orientated back towards platinum. Other [Pt(NRCH2CH2Net2)X(L)] complexes are considered to have similar stereochemistry on the basis of comparison of spectroscopic data, particularly 3JPt,H(py) and 3JPt,H(CH2) coupling constants.

Organoamidometallics. V. Syntheses of [N,N-diethyl-N'-polyfluorophenyl-ethane-1,2-diaminato(1-)]platinum(II) Complexes by Decarboxylation Reactions, and the X-Ray Crystal Structure of trans-[Pt(NC6F5CH2CH2Net2)I(Py)]

Crystals of the title compound are triclinic, with a= 10.299(5), b= 9.289(5), c= 6.841 (4)A, α= 88.98(4), β= 105.57(5), γ= 84.81 (4)°, Z= 2, and space group P. The structure was solved by conventional Patterson and Fourier methods and refined by least-squares techniques to R 0.061 for 1 325 reflections collected by diffractometer. The complex has a planar C,Hg,N,N′ group with unsymmetrically chelated 2,2′-bipyridyl and three-co-ordinate mercury: Hg–C 2.07(5), Hg–N 2.24(3), and Hg–N′2.43(3)A; C–Hg–N 164(1),C–Hg–N′126(1), and N-Hg-N′(chelate angle) 69(1)°. The nitrate ion is regular and unto-ordinated.

Crystal and molecular structure of (2,2′-bipyridyl)methylmercury(II) nitrate, a complex with irregular three-co-ordination

We have determined the structure of [PhHg(C4H7N30)][N03].H20. The crystal is made up of [PhHgNC(NH2)(Me)CH2CO]+ cations containing the phenylmercury group bonded to the ring N atom, nitrate ions, and water molecules. The creatinine and phenyl rings in the cation are almost coplanar, and the cations are stacked with phenyl and creatinine rings of adjacent ions almost parallel and 3·372 A apart. Bond lengths within the creatinine ring indicate delocalization of the carbonyl C(1)O with the guanidinium moiety as the C(1)-N(3) distance, 1·38 (4) A, is appropriate for multiple-bond character.

Organometallic compounds containing a guanidinium group. Crystal and molecular structure of (creatinine)phenylmercury(II) nitrate monohydrate

Treatment of 2-hydroxymethylene-6-methoxy-3,4-dihydronaphthalen-1(2H)-one (13a) with p-meth-oxyphenyllead triacetate afforded 93% of 2-formyl-6-methoxy-2-(p-methoxyphenyl)-3,4-dihydro- naphthalen-1(2H)-one (14a) which upon deformylation and methylation gave 60% of 6-methoxy- 2-(p-methoxyphenyl)-2-methyl-3,4-dihydronaphthalen-1(2H)-one (17). An alternative route to the α α'-disubstituted ketone (17) by way of 6-methoxy-2-methyl-3,4-dihydronaphthalen-1(2H)-one (15) and 2-chloro-6-methoxy-2-methyl-3,4-dihydronaphthalen-1(2H)-one (16) was less efficient. Lithium aluminium hydride reduction of the ketone (17) followed by acetylation yielded 80% of 1 ξ acetoxy- 6-methoxy-2-(p-methoxyphenyl)-2-methyl-1,2,3,4-tetrahydronaphthalene (23), treatment of which with the trimethylsilyl enol ether of ethyl 2-methylpropanoate in the presence of zinc iodide afforded 71% of ethyl (1SR,2RS)-2-methyl-2-[6'-methoxy-2'-(p-methoxyphenyl)-2'-methyl-1',2 ',3',4'-tetrahydronaphthalen-yl'ξ-yl]propanoate (26a). Treatment of the ester (26a) or the corresponding acid (26b) with methanesulfonic acid yielded 68 or 82% respectively, of 2*-dimethoxy-5,5,10b-trimethyl- cis-4b,10b,11,12-tetrahydrochrysen-6(5H)-one (27a); Clemmensen reduction of this followed by demethylation with hydrobromicacidin aceticacid gave 49% of cis-5,5,10b-trimethyl-4b,5,6,10b,11,12- hexahydrochrysene-2,8-diol (7a). The sterochemistry of the ring junction in compound (7a) was established by X-ray crystallography of the corresponding dimethyl ether (27b).

The structure and function of oestrogens. VIII. Synthesis of 5,5, 10b-Trimethyl-cis-4b,5,6,10b,11,12-hexahydrochrysene-2,8-diol from 6-Methoxy-3,4-dihydronaphthalen-1(2H)-one

Bryan M. Gatehouse

Papers

Methyleneketenes and methylenecarbenes. XVI. The formation of Diphenylfuran-2-ones and 3-Phenylphthalide as minor products of the pyrolysis of diphenylmethyl propiolate

Organoamidometallics. V. Syntheses of [N,N-diethyl-N'-polyfluorophenyl-ethane-1,2-diaminato(1-)]platinum(II) Complexes by Decarboxylation Reactions, and the X-Ray Crystal Structure of trans-[Pt(NC6F5CH2CH2Net2)I(Py)]

Crystal and molecular structure of (2,2′-bipyridyl)methylmercury(II) nitrate, a complex with irregular three-co-ordination

Organometallic compounds containing a guanidinium group. Crystal and molecular structure of (creatinine)phenylmercury(II) nitrate monohydrate

The structure and function of oestrogens. VIII. Synthesis of 5,5, 10b-Trimethyl-cis-4b,5,6,10b,11,12-hexahydrochrysene-2,8-diol from 6-Methoxy-3,4-dihydronaphthalen-1(2H)-one