scheme 2 outlines the preparation of efavirenz using an alternative process which is a chiral addition reaction the new chiral addition reaction allows for the elimination of the protection deprotection sequence as outlined in scheme 1 scheme 3 describes the process for the synthesis of the chiral intermediate used in the preparation of efavirenz this reaction has been demonstrated to work using about 1 2 equivalents of cyclopropylacetylene and chiral additive much lesss than the prior methods the numerous chiral additives have been run and give high yields with a commerically available chiral ligand such as n methyl ephedrine and n pyrrolidinyl norephedrine the cyclization of the amino alcohol 3 to produce the 1 4 dihydro 2h 3 1 benzoxazin 2 one 4 is outlined in scheme 4 below the reaction can be carried out as a one step process or alternatively a two step process with the potential isolation of the intermediate carbamate 5 depending upon the chloroformate utilized it has been demonstrated that the aryl chloroformates form less stable carbamates such that when they are treated with aqueous base they cyclize to the product in a one step process the alkyl chloroformate alternatively provides an alkyl carbamate a key intermediate capable of being isolated and purified prior to carrying out the cyclization step based upon the stability of the alkyl carbamates a viable two step.