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Science of Synthesis Knowledge Updates 2014 Vol. 4

Georg Thieme Verlag KGerschienen am01.07.2015
The Science of Synthesis Editorial Board, together with the volume editors and authors, is constantly reviewing the whole field of synthetic organic chemistry as presented in Science of Synthesis and evaluating significant developments in synthetic methodology. Four annual volumes updating content across all categories ensure that you always have access to state-of-the-art synthetic methodology.mehr
EUR2.999,99

Produkt

KlappentextThe Science of Synthesis Editorial Board, together with the volume editors and authors, is constantly reviewing the whole field of synthetic organic chemistry as presented in Science of Synthesis and evaluating significant developments in synthetic methodology. Four annual volumes updating content across all categories ensure that you always have access to state-of-the-art synthetic methodology.
Details
Weitere ISBN/GTIN9783131763518
ProduktartE-Book
EinbandartE-Book
FormatEPUB
Erscheinungsjahr2015
Erscheinungsdatum01.07.2015
Seiten520 Seiten
SpracheEnglisch
Dateigrösse20152
Artikel-Nr.1530755
Rubriken
Genre9200

Inhalt/Kritik

Leseprobe
5.2.17.9 Acylstannanes (Including S, Se, and Te Analogues) (Update 2014)

P. B. Wyatt
5.2.17.9.1 Applications of Acylstannanes in Organic Synthesis 5.2.17.9.1.1 Method 1: Synthesis of β,γ-Unsaturated Ketones by Acylation of Allylic Esters with Acylstannanes
Acylstannanes 1 react with allyli esters 2 in the presence of palladium(II) trifluoroacetate as catalyst to provide good yields of β,γ-unsaturated ketones 3 (ⶠScheme 1).[1] Similar transformations may be achieved using acylsilanes in place of acylstannanes;[2] however, for introduction of the benzoyl group, the tin reagents provide much higher yields than their silicon counterparts, as well as a greatly reduced risk of isomerization to form the α,β-un-saturated isomers of the ketone products.


Scheme 1 Synthesis of β,γ-Unsaturated Ketones[1]

R1 R2 R3 Temp(°C) Yield(%) Ref Ph Me H rt 76 [1] (CH2)5Me Me H 50 71 [1] Ph Bu H rt 64 [1] Ph Me Ph rt 50 [1] (E)-1,4-Diphenylbut-3-en-1-one (3, R1 = R3 = Ph); Typical Procedure:[1]
A mixture of acylstannane 1 (R1 = Ph; R2 = Me; 121 mg, 0.50 mmol; as reported), allylic trifluoroacetate 2 (R3 = Ph; 115 mg, 0.50 mmol), Pd(OCOCF3)2 (8.0 mg, 0.025 mmol), and THF (0.25 mL) was stirred under argon at rt for 8 h. The product 3 was isolated following column chromatography (silica gel, hexane/EtOAc 9:1); yield: 50%.
5.2.17.9.1.2 Method 2: Synthesis of α-Oxoamides by Reaction of Stannanecarboxamides with Acyl Chlorides
The stannanecarboxamide 4 readily couples with acyl chlorides 5 to form α-oxoamides 6 (ⶠScheme 2); no catalyst is needed.[3] Use of dichlorides, such as oxalyl chloride, allows polycarbonyl compounds to be prepared.


Scheme 2 Synthesis of α-Oxoamides by Reaction of Stannanecarboxamides with Acyl Chlorides[3]

R1 Temp(°C) Time(h) Yield(%) Ref Me rt 1 83 [3] iPr rt 1 87 [3] (E)-CH=CHPh rt 1 85 [3] Ph rt 3 85 [3] (CF2)2CF3 60 1 76 [3] N,N-Diisopropyl-2-oxopropanamide (6, R1 = Me); Typical Procedure:[3]
At rt, to a soln of iPr2NCOSnMe3 (4; 1.1 mmol) and docosane (0.37 mmol, internal standard for GC analysis) in benzene (2 mL) (CAUTION: carcinogen) was added AcCl (1.0 mmol) over 10 min and the soln was stirred at rt for 1 h. Volatiles were evaporated and the residue was subjected to column chromatography (silica gel, hexane then CH2Cl2) to give 2-oxoamide 6 (R1 = Me) as a colorless oil; yield: 83%.
5.2.17.9.1.3 Method 3: Synthesis of 3-(Trialkylstannyl)alk-2-enamides by Carbamoylstannylation of Terminal Alkynes
Terminal alkynes 7 undergo carbamoylstannylation upon treatment with the stannane-carboxamide 4 in the presence of a rhodium catalyst [Rh(acac)(CO)2] (ⶠScheme 3).[4] This process is highly regioselective; in the products 8, the carbamoyl group has been added to the terminus of the original alkyne; the reaction is also highly stereoselective (syn addition).


Scheme 3 Synthesis of 3-(Trialkylstannyl)alk-2-enamides by Carbamoylstannylation of Terminal Alkynes[4]

R1 Yielda(%) Regioselectivity(%) Ref Bu 78 99 [4] t-Bu 81 100 [4] Ph 70 100 [4] a GC yield based on the amount of 4 used. 5.2.17.9.1.4 Method 4: Synthesis of 1,4-Dicarbonyl Compounds by Acylstannylation of α,β-Unsaturated Carbonyl Compounds
syn Addition of acylstannanes to alk-2-ynoate esters 9 occurs in the presence of bis(cycloocta-1,5-diene)nickel(0) [Ni(cod)2] as catalyst (ⶠScheme 4). The major products 10, corresponding to acylation at the more electrophilic β-carbon of the Câ¡C bond, are favored over regioisomers 11.


Scheme 4 Synthesis of 1,4-Dicarbonyl Compounds by Acylstannylation of Alk-2-ynoate Esters[5]

R1 R2 R3 R4 Time (h) Ratio (10/11) Yield (%) Ref Ph Me (CH2)4Me Me 2.5 88:12 66 [5] Ph Me TMS Et 3 98:2 85 [5] Ph Me Me Me 1.5 91:9 56 [5] Ph Me Ph Et 24 66:34 58 [5] Et Bu (CH2)4Me Me 24 79:21 47 [5]
Acylation of enones 12 is also possible (ⶠScheme 5); in this case tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3] has higher catalytic activity than bis(cycloocta-1,5-diene)nickel(O) and tin-containing products are not isolated. It has been proposed[5] that the reaction generates a transient metal enolate species 13 (e.g., M = PdSnBu3), which is protonated by stoichiometric quantities of added water to give 1,4-diketones 14, or which may alternatively be trapped by an added aldehyde to give aldol products 15.


Scheme 5 Synthesis of 1,4-Dicarbonyl Compounds by Acylation of Enones[5]

R1 R2 R3 Time (h) Yield (%) Ref Ph Bu Me 2 71 [5] Et Bu Me 3 52 [5] Et Bu Ph 2 39 [5] R1 R2 R3 R4 Time (h) dr Yield (%) Ref Ph Bu Me 4-F3CC6H4 1.5 73:27 64 [5] Et Bu Me 4-F3CC6H4 1 51:49 62 [5] 5.2.17.9.1.5 Method 5: Synthesis of ε-Oxoallylstannanes by Acylstannylation of 1,3-Dienes
Acylstannanes 16 add to 1,3-dienes 17 in a 1,4-sense, in the presence of bis(cycloocta-1,5-diene)nickel(0) as catalyst, to yield ε-oxoallylstannanes 18 and 19 (ⶠScheme 6). Regioselectivity is modest in examples where unsymmetrical dienes 17 are used.


Scheme 6 Synthesis of ε-Oxoallylstannanes by Acylstannylation of 1,3-Dienes[6]

R1 R2 R3 R4 Time (h) Ratio (18/19) Yield (%) Ref Ph Me H H 0.2 - 72 [6] Ph Me Me Me 2 - 73 [6] Ph Me Me H 2 33:67 74 [6] Ph Me Ph H 2 47:53 68 [6] Ph Me (CH2)4 24 - 45 [6] Et Bu Me Me 24 - 56 [6] 1-piperidyl Bu Me Me 2 - 73 [6] 5-Oxoalk-2-enylstannanes 18 and 19 (R1 = Ph);...mehr

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