Nature Chemistry

Table 1 Optimization of the synthesis of compound 1a

From: 2-Oxabicyclo[2.1.1]hexanes as saturated bioisosteres of the ortho-substituted phenyl ring


Entry	Conditions	Yield (%)^a,b
1	419 nm, CH₃CN	n.d.
2	368 nm, CH₃CN	<5
3	313 nm, CH₃CN	<5
4	254 nm, CH₃CN	<20
5	Hanovia mercury lamp, CH₃CN	39
6	368 nm, CH₃CN, PhC(O)Me	47
7	368 nm, CH₃CN, Ph₂CO	81 (56)^c
8	368 nm, CH₃CN, (p-MeOC₆H₄)₂CO	61
9	368 nm, CH₃CN, (p-NO₂C₆H₄)₂CO	38
10	368 nm, CH₂Cl₂, Ph₂CO	71
11	368 nm, Me₂CO, Ph₂CO	68
12	368 nm, PhMe, Ph₂CO	42
13	368 nm, EtOAc, Ph₂CO	29
14	No light, rt	n.d.
15	No light, reflux	n.d.

^aReactions were performed on a 20 mmol scale. ^bThe ¹H-NMR yield of the major isomer (CH₂Br₂ as an internal standard). ^cIsolated yield of major stereoisomer of 1a. rt, room temperature; λ, wavelength; n.d., not determined.

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