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Functionalised cis ‐Alkenes from the Stereoselective Decomposition of Diazo Compounds, Catalysed by [RuCl(η 5 ‐C 5 H 5 )(PPh 3 ) 2 ]
Author(s) -
Del Zotto Alessandro,
Baratta Walter,
Verardo Giancarlo,
Rigo Pierluigi
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200008)2000:15<2795::aid-ejoc2795>3.0.co;2-8
Subject(s) - chemistry , diazo , carbene , stereoselectivity , yield (engineering) , medicinal chemistry , catalysis , ketone , decomposition , organic chemistry , materials science , metallurgy
A catalytic amount of [RuCl(η 5 ‐C 5 H 5 )(PPh 3 ) 2 ] ( 1 ) (0.1 mol‐%) at 60 °C stereoselectively decomposes α‐diazo carbonyl compounds N 2 CHCOR [R = EtO, Me, Et, n Pr, i Pr, Ph, (CH 2 ) 10 Me, and (CH 2 ) 14 Me] affording quantitatively RCOCH=CHCOR carbene dimers [R = EtO ( 10 ), Me ( 11 ), Et ( 12 ), n Pr ( 13 ), i Pr ( 14 ), Ph ( 15 ), (CH 2 ) 10 Me ( 16 ), and (CH 2 ) 14 Me ( 17 )]. The cis isomer is formed in 95−99% purity, depending on the R group. Under the same experimental conditions, N 2 CHCOR 1 and N 2 CHCOR 2 react in equimolar amounts to give mixtures of unsymmetrical cis ‐R 1 COCH=CHCOR 2 ( 18−32 ), and symmetrical cis ‐R 1 COCH=CHCOR 1 and cis ‐R 2 COCH=CHCOR 2 alkenes. The unsymmetrical cis ‐alkenes 23−32 are formed in about 50% yield from the reaction between two α‐diazo ketones. The yield of the cis ‐R 1 COCH=CHCOR 2 compounds 18−22 increases to ca. 60% when a mixture of α‐diazo ketone and N 2 CHCOOEt is catalytically decomposed. Higher conversions into the unsymmetrical products have been obtained by treating N 2 CHCOR and N 2 CHSiMe 3 , from which cis ‐RCOCH=CHSiMe 3 derivatives 34−41 are formed in 83−91% yield. The catalytic decomposition of α,ω‐bis(diazo) ketones N 2 CHCO(CH 2 ) n COCHN 2 ( n = 4, 8, or 10) has also been investigated, and found to afford cyclic cis ‐alkenes arising from both intra‐ [ n = 4 ( 45 ), 8 ( 46 ), and 10 ( 47 )] and intermolecular carbene‐carbene coupling processes.