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Pd‐Catalyzed Reactions of Donor−Acceptor‐Substituted Cyclopropanes and Their Ring‐Opened Derivatives: Attempted Heck Cyclization and Novel One‐Pot Enolate Arylations
Author(s) -
Khan Faiz Ahmed,
Czerwonka Regina,
Reissig HansUlrich
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(200011)2000:21<3607::aid-ejoc3607>3.0.co;2-n
Subject(s) - chemistry , ring (chemistry) , catalysis , heck reaction , acceptor , palladium , combinatorial chemistry , medicinal chemistry , organic chemistry , physics , condensed matter physics
Donor−acceptor substituted cyclopropane derivatives 4a−g were synthesized in good yields from ketones, via the corresponding silyl enol ethers 2a−g , by cyclopropanation with methyl diazoacetate followed by alkylation using o ‐iodobenzyl iodide. The γ‐oxo esters 5a−g were prepared in high yield, employing NEt 3 · 3 HF. A novel Pd‐catalyzed one‐pot transformation of 4a−f into 1,2‐disubstituted indanes 6a−f was accomplished using either CsF (Method A or B) or Bu 4 NF (Method C) as the fluoride source to achieve the in situ ring‐opening of 4a−f . The two reagents CsF and Bu 4 NF function in a complementary manner. For example, CsF works better with enones 4b and 4c , while Bu 4 NF functions well with aryl/alkyl ketones 4d−f . Pd‐catalyzed Heck cyclization of vinyl ketone 5a furnished mainly the 7‐ exo ‐trig cyclization product 7 but isopropenyl ketone 5b gave a moderate yield of indane derivative 6b , arising from enolate arylation. When the carbonyl group in 5b was protected, a novel tricyclic compound 13 was obtained in low yield.