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New adventures with divalent carbon intermediates
Author(s) -
Marchand Alan P.,
Rajagopal D.,
Kumar Kaipenchery A.,
Eckrich Ralf,
Ramanaiah K. C. V.,
Namboothiri I. N. N.,
Alihodžić Sulejman,
Dong Eric Zhiming,
Shukla Rajesh,
Bott Simon G.,
Mlostoń Grzegorz,
Galindo Alberto,
Bartnik Romuald
Publication year - 1998
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19981340111
Subject(s) - chemistry , ylide , cyclohexene , dichlorocarbene , ring (chemistry) , carbon fibers , carbon atom , reactive intermediate , stereochemistry , medicinal chemistry , organic chemistry , materials science , catalysis , composite number , composite material
Part I : Reactions of 3‐substituted 1‐azabicyclo[1.1.0]butanes ( 1a and 1b ) with dichlorocarbene proceed in each case via nitrogen ylide intermediates with concomitant ring opening to afford the corresponding dihaloimines ( 2a and 2b , respectively). Part II : Vinylidènecarbene‐cycloalkyne equilibria have been studied in three polycarbocyclic systems, i.e., 10a ‐ 10b , 20a ‐ 20b , and 27a ‐ 27b . In all three systems, only the vinylidenecarbene intermediate can be trapped in situ by cyclohexene. The results of site‐specific 13 C labeling studies that employ 9 ‐C(8)‐ 13 CBr 2 (enriched with 4 atom‐% 13 C), 19 ‐C(4)‐ 13 CBr 2 (enriched with 5 atom‐% 13 C), and 23 ‐C(4)‐ 13 CBr 2 (enriched with 10 atom‐% 13 C) also support this conclusion and suggest that cycloalkyne intermediates, if formed in these systems, must rearrange very rapidly to the corresponding (thermodynamically favored) vinylidenecarbenes. Part III : Base‐promoted reactions of N ‐tosyl‐ and N ‐benzhydrylazetidin‐3‐ones (i.e., 30a and 30b , respectively) with diethyl diazomethylphosphonate (DAMP), when performed in the presence of cyclohexene, in each case afford exclusively the product that results via in situ trapping of the corresponding vinylidenecarbene.