Sorry to say that making another investment does not change the fact that the sale of your stock and other items will be subject to tax on the gain.
Rather than sell it is possible to use a Like Kind Exchange that involves business or investment property which is exchanged for like kind property. Like Kind Exchanges must not involve constructive receipt of cash for the property relinquished so a qualified intermediary facilitates the exchange using escrow accounts. The proceeds are used to purchase replacement property of like kind and the gain from the property exchanged is deferred into the acquired property.
However, this may or may not fit well in your circumstances as only property used in business and not stocks can qualify for this treatment. For more information and the restrictions see http://www.irs.gov/uac/Like-Kind-Exchanges-Under-IRC-Code-Section-1031
Other than using an exchange one technique to reduce tax in the year of gain is to also sell during the year other property (such as stocks) that would generate a loss to offset the gain. Since in most years a loss can not be fully used to offset other income often the year of gain is the best time to dispose of property that has a loss.
If you and the buyer agree it can be beneficial to use an installment sale and get the proceeds of the sale in more than one tax year. In that case your gain is able to be spread over more than one tax year and there may be less impact as smaller gain in each year is less likely to push your income to higher tax brackets. Whether this will be effective in your circumstance likely will require all of the facts and circumstances to be reviewed and analyzed by an experienced tax practitioner. For more information see http://www.irs.gov/taxtopics/tc705.html
If you have (or you create) a retirement plan in connection with your business it is likely beneficial to contribute up to the maximum to that plan and thereby defer some of your income for the year of the sale. Various plans are available depending on your business as explained in the publication at http://www.irs.gov/pub/irs-pdf/p3998.pdf
Similarly, if you (or your spouse when filing jointly) contribute more to a retirement plan with an employer there can be deferral of income tax on that contribution.
Lastly, in any year when there is an increase of income it may be beneficial to accelerate deductions into that tax year. For example, increased charitable contributions and payment in this year rather than next year of items such as property tax are better used in the year that is subject to a higher marginal tax rate.
Hopefully these items can help your goal to defer or reduce the income tax on the sale and as you confer with a tax professional to apply the concepts to your situation.
Please ask if you need more discussion or clarification.