✍ Scribed by Dr. Alan J. Jones; Dr. P. J. Garratt; Dr. K. Peter C. Vollhardt
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yield, m. p. 106"C), and ( 4 ) (125 hours' heating in benzene, 73% yield, m. p. 86 "C), respectively.
Steroidal diazo ketones also undergo this rearrangement. Thus in 2 h at 40"C, 2-diazo-5~1-cholestan-3-one~~~ and a large excess of dimethyl acetylenedicarboxylate afford the steroidal pyrazole ( 5 ) (m.p. 204°C) in 61% yield.
form colorless crystals and show no N=N absorption in the ultraviolet region but only a shoulder at 235nm (~=6000-7000). The NMR spectra (6/TMS) of ( I ) , (Z), and ( 5 ) indicate two different methyl ester groups (two singlets near 3.90ppm) and one CH2 group CI to the amide and another 01 to the pyrazole: ( I ) 2.77 and 3.38ppm (broad triplet, J=6Hz); (2) 2.96 and 3.35 ppm (complex multiplet); ( 5 ) strongly shielded protons at 3.0 and 3.5 ppm (4H), together with the typical steroid portion of the spectrum.
The spectra of the bridged heterocycles ( 3 ) and (4) resemble those of ( 1 ) and (2), each having only two or one CH group: ( 3 ) 3.44 and 4.24ppm (complex multiplets); ( 4 ) 3.79 ppm (1 H, broad doublet, 3 = 6 Hz).
📜 SIMILAR VOLUMES
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Antarafacial 1,3-sigmatropic shifts in carbonyl derivatives of PH 2 Ͼ F Ͼ OCH 3 Ͼ OH Ͼ SiH 3 Ͼ H Ͼ C 6 H 5 Ͼ CH 3 . The barrier heights range from 10 kcal/mol for Cl migration to 35 ketenes, isocyanates, thioketenes and thioisocyanates have been studied by means of ab initio MO calculations. Energy
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